We have reviewed the outcome of a low-dose step-up regimen for induction of ovulation in clomiphene-unresponsive women with PCOS and in women with hypothalamic hypogonadism (HH), treated at a single centre. Data from 366 women with PCOS and 80 with HH (1165 records) were entered into a FileMakerPro database, refined and constrained to allow stratification and analysis of relevant data. 85% of cycles were ovulatory in both PCOS and HH. PCOS patients were more likely to have cycles characterised by single follicle development than were women with HH (57% vs 42%, p=0.0003) whereas cycles cancelled because of multiple follicle development were more common in women with HH (37% v 19%, p<0.0001). Women with HH needed a higher threshold (maximum daily) dose of FSH than PCOS women to achieve ovulation (median dose 132iu/day v 75iu/day, p<0.0001) but the cumulative conception rate was higher in HH than in PCOS (65% v 49%, p=0.0007). The prevalence of multiple pregnancies was low in both groups (PCOS 0.01% cycles, 4% of pregnancies; HH 0.04% cycles, 5% of pregnancies). In summary, despite the need for higher doses of FSH and an increased risk of multiple follicle development in women with HH, a low-dose gonadotrophin regimen is equally effective in women with PCOS and HH in terms of ovulation rate and low frequency of multiple pregnancies. The lower pregnancy rate in women with PCOS is likely to reflect the fact that these women, by definition, had received previous treatment for induction of ovulation (and some had ovulated without conceiving and were more likely to have other, confounding causes of subfertility) whereas those with HH had not previously received treatment.