This multicentre, open, randomized, study compared the efficacy and safety of recombinant follicle stimulating hormone (rFSH; follitropin alpha) with highly purified urinary human FSH (uFSH; urofollitropin HP) in women undergoing ovulation induction for assisted reproductive techniques. Following long down-regulation with buserelin, patients received two ampoules of 75 IU (150 IU) s.c. rFSH or highly purified uFSH for 6 days, after which the dose could be increased until they fulfilled the criteria for human chorionic gonadotrophin (HCG) administration. Of 168 patients recruited, 155 received at least one dose of FSH, and 137 received HCG [68: rFSH (85%); 69: uFSH (92%)]. Following oocyte retrieval and fertilization, up to three embryos were replaced/patient and luteal support was given. The mean number of oocytes retrieved/patient was 10.2 +/- 6.0 for rFSH patients compared with 10.8 +/- 6.1 in the uFSH group (not significant). There was a trend towards fewer ampoules used (22.3 +/- 6.5 versus 24.3 +/- 6.5), higher pregnancy (44.3 versus 41.4%) and live birth rates (33.8 versus 26.7%), as well as a lower miscarriage rate (0.0 versus 16.7%) in favour of rFSH. However, no significant differences in efficacy parameters were recorded. Ovarian hyperstimulation syndrome occurred in 8.6% and 7.9% of rFSH and uFSH patients respectively. In conclusion, this protocol was effective in inducing multiple follicular development and high numbers of oocytes were retrieved with both drugs.