SummarySerum levels of follicle stimulating hormone (FSH) and luteinizing hormone (LH) were measured daily for 10 days from the 7th day of the menstrual cycle in 15 healthy Yoruba women, six of whom had singleton infants, seven of whom had had one set of twins, and two of whom had had two sets of twins.Mean FSH levels were higher at the peak and for four days before and after the peak in women who had had twins, compared to those who had had singletons, and higher still in the women who had had two sets of twins. Mean LH levels and the height of the LH peak were less clearly related to the twinning history.