Forty-two women with primary dysmenorrhea were successfully enrolled in a double-blind, three-way crossover study in which each patient received either ibuprofen (Motrin), indomethacin (Indocin), or a placebo during each of three successive painful menstrual cycles. Thirty-one patients successfully completed the study. The results showed that ibuprofen and indomethacin were superior to the placebo in their ability to relieve pain and that patients preferred ibuprofen to indomethacin. Ibuprofen was significantly superior to the placebo regarding the number of patients who could pursue normal daily function, whereas indomethacin was not. Four patients reported side effects, all during the indomethacin cycle.