diff --git a/libserialport.h.in b/libserialport.h.in
index fa5ba1a..12e9cba 100644
--- a/libserialport.h.in
+++ b/libserialport.h.in
@@ -109,6 +109,16 @@ enum sp_mode {
 	SP_MODE_NONBLOCK = 4,
 };
 
+/** Buffer selection. */
+enum sp_buffer {
+	/** Input buffer. */
+	SP_BUF_INPUT = 1,
+	/** Output buffer. */
+	SP_BUF_OUTPUT = 2,
+	/** Both buffers. */
+	SP_BUF_BOTH = 3,
+};
+
 /** Parity settings. */
 enum sp_parity {
 	/** Special value to indicate setting should be left alone. */
@@ -506,12 +516,14 @@ enum sp_return sp_read(struct sp_port *port, void *buf, size_t count);
 enum sp_return sp_write(struct sp_port *port, const void *buf, size_t count);
 
 /**
- * Flush serial port buffers.
+ * Flush serial port buffers. Data in the selected buffer(s) is discarded.
+ *
+ * @param buffers Which buffer(s) to flush.
  *
  * @return SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG
  *         if an invalid port is passed.
  */
-enum sp_return sp_flush(struct sp_port *port);
+enum sp_return sp_flush(struct sp_port *port, enum sp_buffer buffers);
 
 /**
  * @}
diff --git a/serialport.c b/serialport.c
index 353cd34..92156b4 100644
--- a/serialport.c
+++ b/serialport.c
@@ -505,17 +505,31 @@ enum sp_return sp_close(struct sp_port *port)
 	return SP_OK;
 }
 
-enum sp_return sp_flush(struct sp_port *port)
+enum sp_return sp_flush(struct sp_port *port, enum sp_buffer buffers)
 {
 	CHECK_PORT();
 
 #ifdef _WIN32
+	DWORD flags = 0;
+	if (buffers & SP_BUF_INPUT)
+		flags |= PURGE_RXCLEAR;
+	if (buffers & SP_BUF_OUTPUT)
+		flags |= PURGE_TXCLEAR;
+
 	/* Returns non-zero upon success, 0 upon failure. */
-	if (PurgeComm(port->hdl, PURGE_RXCLEAR | PURGE_TXCLEAR) == 0)
+	if (PurgeComm(port->hdl, flags) == 0)
 		return SP_ERR_FAIL;
 #else
+	int flags = 0;
+	if (buffers & SP_BUF_BOTH)
+		flags = TCIOFLUSH;
+	else if (buffers & SP_BUF_INPUT)
+		flags = TCIFLUSH;
+	if (buffers & SP_BUF_OUTPUT)
+		flags = TCOFLUSH;
+
 	/* Returns 0 upon success, -1 upon failure. */
-	if (tcflush(port->fd, TCIOFLUSH) < 0)
+	if (tcflush(port->fd, flags) < 0)
 		return SP_ERR_FAIL;
 #endif
 	return SP_OK;