This paper highlights the difficulties of recruiting subjects to objective menstrual blood loss (MBL) studies. Such difficulties may explain the relative paucity of such studies in the literature. Eleven women with objectively assessed evidence of menorrhagia were treated for 1 month with an induction dose of 200 mg of danazol (Danocrine). Subsequently the women were randomly assigned to receive 50, 100 or 200 mg of danazol or placebo for 2 months of maintenance dosing. Follow-up with objective assessment of MBL was continued for 3 months after cessation of maintenance dosing. Danazol 200 mg as an induction dose significantly reduced MBL. The maintenance dose of 200 mg during the following 2 months produced a further decrease in MBL and in some cases amenorrhoea. The lower maintenance dosages of 50 mg and 100 mg were associated with a variable response. The study was unable to determine whether any beneficial effect of the maintenance dosages of danazol could be maintained following cessation of therapy since the study numbers had become too small. It appears, however, that there is unlikely to be any persisting benefit once therapy has ceased.