It has been postulated that venous thrombosis in free flap surgery necessitates the use of 2 venous anastomoses into different venous systems. We retrospectively analyzed a single surgeon's 10-year experience (August 1993 to August 2003) in primary free flap reconstruction for malignant tumors of the head and neck. Of 492 primary reconstructions that did not need a vein graft, vein loop, or cephalic turnover procedure, 251 used the internal jugular venous system as venous outflow, 140 used the subclavian system as outflow, and 101 used both. Two hundred thirty-eight of 251 (95%) of flaps utilizing the internal jugular venous system for outflow were successful compared with 129 of 140 (92%) of flaps utilizing the subclavian system. Where both venous systems were used the success rate was 101 of 101 (100%) (P < 0.05). Where possible, a second venous anastomosis should be performed utilizing both venous drainage systems.