We investigated whether a recombinant follicle stimulating hormone (FSH) (Puregon) can be administered less frequently and at lower doses during ovulation induction than is current practice. Patients (20-35 years, body mass index <30 kg/m(2)) with infertility and chronic anovulation secondary to polycystic ovarian syndrome and resistant to previous clomiphene treatment received (Puregon); 100 IU, n = 17 patients, or 50 IU, n = 10 patients) on alternate days. After 2 weeks and in the absence of follicular recruitment, doses were increased stepwise at weekly intervals (50 IU/alternate days). Twenty-two cycles out of 27 were ovulatory. There were six pregnancies, five from Puregon (100 IU) and one from Puregon (50 IU); four pregnancies proceeded to term. The duration of stimulation (mean, range) with Puregon (100 IU) was 16.4, 7-29 and Puregon (50 IU) 19.1, 8-38 days. The gonadotrophin doses administered (mean; range) were 689, 200-1800 IU (Puregon 50 IU) and 939, 400-2300 IU (Puregon 100 IU). We conclude that low dose alternate day Puregon treatment is suitable for this difficult patient group.