The potential role of endocrine abnormalities during the follicular phase in women with unexplained recurrent pregnancy loss was investigated in a retrospective study. Eighty women with recurrent pregnancy loss underwent routine work-up to exclude known associations with the condition. Following investigation, 58 women failed to reveal an identifiable cause, and were therefore classified as having unexplained recurrent pregnancy loss. The control group consisted of women with known causes of abortions, such as uterine septum and parental chromosomal abnormalities. Mean age, gravidity, parity, presence of infertility, previous number of miscarriages and duration of marriage were similar in both groups. Day-3 serum levels of follicle stimulating hormone (FSH), estradiol, luteinizing hormone (LH) prolactin, total testosterone, dehydroepiandrosterone sulfate (DHEAS) and thyroid stimulating hormone (TSH) were compared in the two groups. FSH, estradiol, LH, prolactin and DHEAS concentrations were significantly higher in the unexplained recurrent pregnancy loss group than in the explained recurrent pregnancy loss group, although serum concentrations of all hormones were within the normal range (p < 0.01). TSH and total testosterone levels were similar in the two groups (p > 0.05). There were no differences in the frequency of abnormal levels of hormones between the two groups (p > 0.05). We conclude that endocrine abnormalities in the follicular phase are not associated with recurrent pregnancy loss.