Thirty-two amenorrheic patients were treated with a tablet oral placebo preparation for a period varying from 30 to 180 days. Another 24 amenorrheic patients were also treated with a placebo administered i.m. for a period varying from 30 to 120 days. As a consequence of the treatment, 27 patients (48%) had menstrual bleedings. The progestogen withdrawal test responsive patients were more responsive to placebo (73 vs. 14% in the progestogen withdrawal test nonresponsive, p < 0.001). The time lag between starting the medication and the first bleeding varied between 4 and 120 days with a mean value of 3 3.9 (SD 26.3). Oral placebo was more effective than the intramuscular form (56 vs. 38%, p < 0.05).