A series of 45 ovulatory women with a complaint of menorrhagia were randomized into 3 treatment groups, before receiving therapy with mefenamic acid in 2 cycles and 1 of 3 other agents in 2 cycles: naproxen (group 1; n = 14), a low dose monophasic combined oral contraceptive (group 2; n = 12) or low dose danazol (group 3; n = 12). Menstrual blood loss was measured in 2-4 control cycles and during therapy. Mefenamic acid reduced measured blood loss by 20%; 38%; and 39% in groups 1-3 respectively. Naproxen reduced blood loss by 12%; the oral contraceptive by 43%; and danazol by 49%. There was no statistically significant difference in blood loss reduction (mean of 2 cycles) between any of the treatments, although women on danazol experienced a dramatic and highly significant further reduction in blood loss after the first treatment cycle (p less than 0.003). These were all effective therapies in a majority of women, but some 'non-responders' were seen in each group. The 'non-responders' had a significantly lower pretreatment blood loss than responders. Several women in group 1 showed anomalous responses to prostaglandin inhibitors with consistent and substantial exacerbation of menorrhagia during therapy. A number of reasonable therapies exist for the medical treatment of menorrhagia, but because none is suitable for everyone management needs to be individualized for each patient.