diff --git a/src/PinChangeInterrupt.cpp b/src/PinChangeInterrupt.cpp
index bcdd6c3..2a9554b 100644
--- a/src/PinChangeInterrupt.cpp
+++ b/src/PinChangeInterrupt.cpp
@@ -121,6 +121,29 @@ void enablePinChangeInterruptHelper(const uint8_t pcintPort, const uint8_t pcint
 #endif
 	}
 
+	// Special case for Attiny x61 where PCMSK0 and PCMSK1 registers
+	// have initial values of 1 for some reason.
+	// See datasheet section 9.3.4 and 9.3.5
+	// https://ww1.microchip.com/downloads/en/devicedoc/atmel-2588-8-bit-avr-microcontrollers-tinyavr-attiny261-attiny461-attiny861_datasheet.pdf
+#if defined(GIMSK) && (defined(__AVR_ATtiny261__) || defined(__AVR_ATtiny461__) || defined(__AVR_ATtiny861__))
+#if (PCINT_USE_PORT1 == true)
+	// PCIE0 case
+	if (!(GIMSK & (1 << PCIE0))) {
+		// Clear PCINT11:8
+		PCMSK1 &= ~0x0F;
+	}
+	// PCIE1 case
+#endif
+	if (!(GIMSK & (1 << PCIE1))) {
+#if (PCINT_USE_PORT1 == true)
+		// Clear PCINT15:12
+		PCMSK1 &= ~0xF0;
+#endif
+		// Clear PCINT7:0
+		PCMSK0 = 0x00;
+	}
+#endif
+
 	// Pin change mask registers decide which pins are ENABLE as triggers
 #ifdef PCMSK0
 #ifdef PCMSK1
@@ -165,6 +188,21 @@ void enablePinChangeInterruptHelper(const uint8_t pcintPort, const uint8_t pcint
 	PCICR |= (1  << (pcintPort + PCIE0));
 #elif defined(GICR) /* e.g. ATmega162 */
 	GICR |= (1  << (pcintPort + PCIE0));
+#elif defined(GIMSK) && (defined(__AVR_ATtiny261__) || defined(__AVR_ATtiny461__) || defined(__AVR_ATtiny861__))
+    // This is a special case for Attiny x61 series which was very weird PCINT mapping.
+    // See datasheet section 9.3.2: http://ww1.microchip.com/downloads/en/devicedoc/atmel-2588-8-bit-avr-microcontrollers-tinyavr-attiny261-attiny461-attiny861_datasheet.pdf
+#if (PCINT_USE_PORT1 == true)
+    if (pcintPort == 1 && pcintMask < (1 << 4)) {
+        // PCINT11:8 will be enabled with PCIE0
+        GIMSK |= (1 << PCIE0);
+    }
+    else {
+#endif
+        // PCINT7:0 and PCINT15:12 will be enabled with PCIE1
+        GIMSK |= (1 << PCIE1);
+#if (PCINT_USE_PORT1 == true)
+    }
+#endif
 #elif defined(GIMSK) && defined(PCIE0) /* e.g. ATtiny X4 */
 	GIMSK |= (1  << (pcintPort + PCIE0));
 #elif defined(GIMSK) && defined(PCIE) /* e.g. ATtiny X5 */
@@ -247,9 +285,31 @@ void disablePinChangeInterruptHelper(const uint8_t pcintPort, const uint8_t pcin
 	// if that's the last one, disable the interrupt.
 	if (*(&PCMSK + pcintPort) == 0) {
 		disable = true;
-	}
 #endif // ifdef PCMSK0
 
+	// This is a special case for Attiny x61 series which was very weird PCINT mapping.
+	// See datasheet section 9.3.2:
+	// http://ww1.microchip.com/downloads/en/devicedoc/atmel-2588-8-bit-avr-microcontrollers-tinyavr-attiny261-attiny461-attiny861_datasheet.pdf
+#if defined(GIMSK) && (defined(__AVR_ATtiny261__) || defined(__AVR_ATtiny461__) || defined(__AVR_ATtiny861__))
+#if (PCINT_USE_PORT1 == true)
+	if (pcintPort == 1 && pcintMask < (1 << 4)) {
+		//PCINT11:8 will be disabled with PCIE0
+		if (!(PCMSK1 & 0x0F)) {
+			GIMSK &= ~(1 << PCIE0);
+		}
+	}
+	else {
+		//PCINT7:0 and PCINT15:12 will be disabled with PCIE1
+		if (!PCMSK0 && !(PCMSK1 & 0xF0)) {
+#else
+		if (!PCMSK0) {
+#endif
+			GIMSK &= ~(1 << PCIE1);
+		}
+#if (PCINT_USE_PORT1 == true)
+	}
+#endif
+#else
 	if(disable)
 	{
 #ifdef PCICR
@@ -264,6 +324,7 @@ void disablePinChangeInterruptHelper(const uint8_t pcintPort, const uint8_t pcin
 #error MCU has no such a register
 #endif
 	}
+#endif
 }
 
 /*
diff --git a/src/PinChangeInterrupt0.cpp b/src/PinChangeInterrupt0.cpp
index e95da51..b48285c 100644
--- a/src/PinChangeInterrupt0.cpp
+++ b/src/PinChangeInterrupt0.cpp
@@ -36,8 +36,17 @@ THE SOFTWARE.
 void attachPinChangeInterrupt0(void) {
 	// fake function to make the IDE link this file
 }
+#ifdef PCINT_COMBINE_PORT0_PORT1
+void attachPinChangeInterrupt1(void) {
+	// fake function to make the IDE link this file
+}
+#endif
 
+#ifdef PCINT_COMBINE_PORT0_PORT1
+ISR(PCINT_vect) {
+#else
 ISR(PCINT0_vect) {
+#endif
 	// get the new and old pin states for port
 	uint8_t newPort = PCINT_INPUT_PORT0;
 
@@ -71,6 +80,42 @@ ISR(PCINT0_vect) {
 #else
 	PCINT_CALLBACK_PORT0
 #endif
+
+#if defined(PCINT_COMBINE_PORT0_PORT1) && (PCINT_USE_PORT1 == true)
+	// get the new and old pin states for port
+	newPort = PCINT_INPUT_PORT1;
+
+	// compare with the old value to detect a rising or falling
+	arrayPos = getArrayPosPCINT(1);
+	change = newPort ^ oldPorts[arrayPos];
+	rising = change & newPort;
+	falling = change & oldPorts[arrayPos];
+
+	// check which pins are triggered, compared with the settings
+	risingTrigger = rising & risingPorts[arrayPos];
+	fallingTrigger = falling & fallingPorts[arrayPos];
+	trigger = risingTrigger | fallingTrigger;
+
+	// save the new state for next comparison
+	oldPorts[arrayPos] = newPort;
+
+	// Execute all functions that should be triggered
+	// This way we can exclude a single function
+	// and the calling is also much faster
+	// We may also reorder the pins for different priority
+#if !defined(PCINT_CALLBACK_PORT1)
+	PCINT_CALLBACK(0, 8);
+	PCINT_CALLBACK(1, 9);
+	PCINT_CALLBACK(2, 10);
+	PCINT_CALLBACK(3, 11);
+	PCINT_CALLBACK(4, 12);
+	PCINT_CALLBACK(5, 13);
+	PCINT_CALLBACK(6, 14);
+	PCINT_CALLBACK(7, 15);
+#else
+	PCINT_CALLBACK_PORT1
+#endif
+#endif // defined(PCINT_COMBINE_PORT0_PORT1) && (PCINT_USE_PORT1 == true)
 }
 
 #if defined(PCINT_API)
@@ -142,6 +187,57 @@ void PinChangeInterruptEventPCINT7(void) {
 }
 #endif
 
+#ifdef PCINT_COMBINE_PORT0_PORT1
+#if (PCINT_USE_PCINT8 == true)
+volatile callback callbackPCINT8 = pcint_null_callback;
+void PinChangeInterruptEventPCINT8(void) {
+	callbackPCINT8();
+}
+#endif
+#if (PCINT_USE_PCINT9 == true)
+volatile callback callbackPCINT9 = pcint_null_callback;
+void PinChangeInterruptEventPCINT9(void) {
+	callbackPCINT9();
+}
+#endif
+#if (PCINT_USE_PCINT10 == true)
+volatile callback callbackPCINT10 = pcint_null_callback;
+void PinChangeInterruptEventPCINT10(void) {
+	callbackPCINT10();
+}
+#endif
+#if (PCINT_USE_PCINT11 == true)
+volatile callback callbackPCINT11 = pcint_null_callback;
+void PinChangeInterruptEventPCINT11(void) {
+	callbackPCINT11();
+}
+#endif
+#if (PCINT_USE_PCINT12 == true)
+volatile callback callbackPCINT12 = pcint_null_callback;
+void PinChangeInterruptEventPCINT12(void) {
+	callbackPCINT12();
+}
+#endif
+#if (PCINT_USE_PCINT13 == true)
+volatile callback callbackPCINT13 = pcint_null_callback;
+void PinChangeInterruptEventPCINT13(void) {
+	callbackPCINT13();
+}
+#endif
+#if (PCINT_USE_PCINT14 == true)
+volatile callback callbackPCINT14 = pcint_null_callback;
+void PinChangeInterruptEventPCINT14(void) {
+	callbackPCINT14();
+}
+#endif
+#if (PCINT_USE_PCINT15 == true)
+volatile callback callbackPCINT15 = pcint_null_callback;
+void PinChangeInterruptEventPCINT15(void) {
+	callbackPCINT15();
+}
+#endif
+#endif // PCINT_COMBINE_PORT0_PORT1
+
 #endif // PCINT_API
 
 #endif // PCINT_USE_PORT0
diff --git a/src/PinChangeInterrupt1.cpp b/src/PinChangeInterrupt1.cpp
index fd90e19..fba7993 100644
--- a/src/PinChangeInterrupt1.cpp
+++ b/src/PinChangeInterrupt1.cpp
@@ -31,7 +31,7 @@ THE SOFTWARE.
 #if defined(PCINT_ALINKAGE) && defined(PCINT_COMPILE_ENABLED_ISR) && defined(PCINT_INCLUDE_FROM_CPP) \
 	|| !defined(PCINT_ALINKAGE) || !defined(PCINT_COMPILE_ENABLED_ISR)
 
-#if (PCINT_USE_PORT1 == true)
+#if (PCINT_USE_PORT1 == true) && !defined(PCINT_COMBINE_PORT0_PORT1)
 
 void attachPinChangeInterrupt1(void) {
 	// fake function to make the IDE link this file
diff --git a/src/PinChangeInterruptBoards.h b/src/PinChangeInterruptBoards.h
index fdcfa65..d3c44f1 100644
--- a/src/PinChangeInterruptBoards.h
+++ b/src/PinChangeInterruptBoards.h
@@ -142,6 +142,10 @@ THE SOFTWARE.
 // PORTB has Reset, clock and SPI while PORTA has I2C and Analog Pins. We just enable all pins.
 #define PCINT_INPUT_PORT0 PINA
 #define PCINT_INPUT_PORT1 PINB
+// Attiny x61 Series has a very special interrupt vector and port mapping.
+// It combines PCINT0_vect and PCINT1_vect into PCINT_vect
+// See datasheet section 9.1: http://ww1.microchip.com/downloads/en/devicedoc/atmel-2588-8-bit-avr-microcontrollers-tinyavr-attiny261-attiny461-attiny861_datasheet.pdf
+#define PCINT_COMBINE_PORT0_PORT1 true
 
 #else // Microcontroller not supported
 #error PinChangeInterrupt library does not support this MCU.
diff --git a/src/PinChangeInterruptPins.h b/src/PinChangeInterruptPins.h
index f000870..93fc33a 100644
--- a/src/PinChangeInterruptPins.h
+++ b/src/PinChangeInterruptPins.h
@@ -371,12 +371,14 @@ Serial.println();
 // Hardware Definitions
 //================================================================================
 
-#if defined(PCINT0_vect)
+//special case for the x61 where a single interrupt vector is used for multiple ports
+#if defined(PCINT0_vect) || (defined(PCINT_vect) && (defined(__AVR_ATtiny261__) || defined(__AVR_ATtiny461__) || defined(__AVR_ATtiny861__)))
 #define PCINT_HAS_PORT0 true
 #else
 #define PCINT_HAS_PORT0 false
 #endif
-#if defined(PCINT1_vect)
+//special case for the x61 where a single interrupt vector is used for multiple ports
+#if defined(PCINT1_vect) || (defined(PCINT_vect) && (defined(__AVR_ATtiny261__) || defined(__AVR_ATtiny461__) || defined(__AVR_ATtiny861__)))
 #define PCINT_HAS_PORT1 true
 #else
 #define PCINT_HAS_PORT1 false