Perfusion dynamics of 16 free DIEP flaps and 4 free SIEA flaps were studied during the first, third, and sixth postoperative day using dynamic infrared thermography (DIRT). For both flap types the zone positioned over the perforator is perfused first, followed by the adjacent ipsilateral zone, and finally the contralateral zones. Perfusion of the subdermal plexus of all zones preceded the perfusion of the subcutaneous layer of all zones. While the initial hyperemia subsided with time, the total number of hot spots increased with time. Perfusion of free DIEP and SIEA flaps during the first postoperative week is a dynamic process. The perfusion shows a stepwise progression at the level of the subdermal plexus and at the level of the subcutaneous layer each with its own time sequence and with the midline as an area of resistance for circulation.