['To compare the safety and efficacy of recombinant FSH (follitropin beta, Puregon; NV Organon, Oss, the Netherlands) and urinary FSH (urofollitropin, Metrodin; Ares-Serono, Geneva, Switzerland).', 'A prospective, multicenter, assessor-blind, randomized, clinical trial.', 'Twelve European infertility clinics.', 'One hundred seventy-two women (recombinant FSH: n = 105; urinary FSH: n = 67) with clomiphene citrate-resistant normogonadotropic chronic anovulation (World Health Organization group II).', 'Eligible subjects were randomized (ratio of recombinant to urinary FSH, 3:2) and treated for a maximum of three cycles. A low-dose step-up regimen was used, with 75 IU of FSH given IM daily for a maximum of 14 days and, if needed, weekly increments of half an ampule given thereafter until the threshold dose for follicular development was achieved.', 'Cumulative ovulation rate after three cycles, total FSH dose, and treatment period needed to achieve ovulation.', 'The cumulative ovulation rates after three treatment cycles were 95% and 96% for the recombinant and urinary FSH groups, respectively. Overall, ovulation was seen in 155 of 223 treatment cycles (69.5%) in the recombinant FSH group, compared with 92 of 138 treatment cycles (66.7%) in the urinary FSH group. In the first cycle, a statistically significantly lower total dose (750 versus 1,035 IU) and a shorter treatment period (10 versus 13 days) were needed in the recombinant FSH group to reach ovulation. Only one case of ovarian hyperstimulation syndrome led to hospitalization. Two sets of twins (one in each treatment group) and one set of triplets (in the recombinant FSH group) were born.'] Is recombinant follicle-stimulating hormone ( FSH ; Puregon ) more efficient than urinary FSH ( Metrodin ) in women with clomiphene citrate-resistant , normogonadotropic , chronic anovulation : a prospective , multicenter , assessor-blind , randomized , clinical trial . European Puregon Collaborative Anovulation Study Group?