Plasma follicle stimulating hormone (FSH) and luteinising hormone (LH) concentrations, and pregnanediol and oestrogen excretion rates, were measured in a perimenopausal woman from the first appearance of oligomenorrhoea until the onset of severe and persistent hot flushes two years later. Postmenopausal episodes characterised by hot flashes, amenorrhoea, high FSH levels (greater than or equal to 5IU/L) and low urinary oestrogens (less than or equal to 50 nmol/24hr), were followed by menstrual cycles in which the FSH levels were low (less than 5 IU/L) and there was an ovulatory pattern of oestrogen and pregnanediol excretion. An unusual association of high urinary oestrogens (greater than or equal to 50 nmol/24hr) with high gonadotrophin levels was observed on several occasions. The transient postmenopausal episodes were biochemically and symptomatically indistinguishable from the permanent amenorrhoea of postmenopausal women.