Parmitano, from the European Space Agency, began the excursion with NASA astronaut Chris Cassidy at 2.00pm central European time. The six-and-a-half hour spacewalk is being broadcast live by NASA (see below).
The walk involves collecting information from experiments that have been conducted, taking photographs and removing and replacing faulty equipment, NASA said. Another space walk will be performed later in July.
Parmitano will not return to earth until November, having left from Kazakhstan on May 30th.
The Italian astronaut has been staying connected to earth with regular updates and photographs from space posted on his Twitter account.
Last month he used his blog to tell the world his delight in receiving a delivery of Italian food.