This study was designed to test the assumption that women with regular menstrual cycles and premenstrual symptoms are ovulatory. Forty women aged 20 to 40 years were selected as probably ovulatory on the basis of their recent histories of regular menstrual cycles consistently accompanied by premenstrual molimina. Each subject recorded menses and basal body temperatures (BBT) for 1-3 consecutive menstrual cycles during which luteal phase serum progesterone (P) concentrations were determined by radioimmunoassay. All subjects were rated ovulatory or anovulatory by each of several espoused P criteria, which confirmed 39/40 subjects (98%) to be ovulatory by a 3 ng/ml criterion, 38/40 subjects (95%) by a 5 ng/ml criterion, and 36/40 (90%) by a 15 ng/ml criterion. Thus, P measurements confirmed the clinical impression of ovulation in 90-98% of subjects depending on which P criterion was selected. Basal body temperatures correlated well with P measurements in that 61/66 cycles (92%) displayed a biphasic BBT pattern, 2/66 cycles (3%) displayed a monophasic BBT pattern, and 3/66 cycles (5%) were uninterpretable. Only 1 subject was not ovulatory in either of 2 consecutive cycles by even the most liberal P criterion, and both cycles were abnormally long and would have been suspected of being anovulatory on clinical grounds. We conclude that patients presenting with a history of regular menstrual cycles accompanied by premenstrual molimina are identifiable as ovulatory without the necessity of measuring luteal phase serum P concentrations.