A retrospective analysis of the records of 107 free flap transplants in 94 patients operated on between May of 1992 and September of 1997 at the Center for Microsurgery of Extremities, Nopparatrajathanee Hospital, was conducted to study the risk factors leading to free flap failure. These factors were periods of operation to reflect the experience of the surgeon, locations of the defects, anastomotic techniques, and the use of vein grafts. Chi-square, Fisher's exact test, and multiple logistic regression analysis were used to determine the significance of the data. The overall vascular complication rate was 28 percent (30 of 107 transplants) and the re-exploration rate was 13 percent (14 of 107 transplants), the flap salvage rate was 50 percent (7 of 14 flaps), whereas the overall failure rate was 15 percent (16 of 107 transplants). The significant factors that caused free flap failure were the experience of the surgeon and the use of vein grafts. The most important experience was in the choice and preparation of the recipient vessel. When the surgeon gained more experience in the past 2 years (from October of 1995 to September of 1997), the success rate improved significantly. Moreover, the use of vein grafts no longer affected the outcome. Therefore, in this investigation the most important factor that improved the outcome of free tissue transplantation in the extremities was the experience of the surgeon in choosing and preparing the recipient vessels.