Although technical refinements have improved microvascular techniques, the problem of vessel-size discrepancy between donor and recipient vessels is still unsolved and can decrease the success rate of free tissue transfer. In fact, if vessels with incongruent diameters are not adequately anastomosed, the risk of free flap failure is increased. In this paper, the authors present a new type of microvascular anastomosis to overcome the problem of vessel-size discrepancy. Interrupted mattress sutures are placed in end-to-end anastomosis narrowing the wider diameter and compensating for the diameter incongruency. The surgical technique and main clinical applications of the interrupted micro-mattress sutures are described in detail. Indications and advantages are discussed.