Tubal ligation is one of the most effective and reliable methods of contraception and of successful program of birth control in Iran. Present study was done to evaluate factors affecting risk of complications during tubal ligation surgery. We studied 1780 women that had tubal ligation in 13 hospitals in Tehran during the years 1993-95. Data on operation were collected by questionnaire and analyzed using logistic regression method. Risk of complications was increased in women had had operation after vaginal therapy, in luteal phase, after cesarean section and in follicular phase, respectively. Modified pomery, pomery and parkland methods of operation were ascendingly related to increased risk of complications. Age, history of pelvic pain, method of anesthesia, incision size and time of operation were not significantly correlated with complications. Frequency of complications was higher in women that had other procedures during surgery. We suggest that tubal ligation be done after vaginal delivery and by modified pomery method.