In a randomized four-way crossover study, 32 women with primary dysmenorrhea were treated with transcutaneous electrical nerve stimulation (TENS) for two cycles, placebo (sham) TENS for one cycle, or ibuprofen 400 mg four times a day for one cycle. The TENS setting used was 100 pulses per second with 100-microsecond pulse widths. The subjects were allowed to adjust the amplitude to a comfortable level. The pain rescue medication was ibuprofen 400 mg as needed, up to 1600 mg/day. Significantly more subjects who had TENS treatment did not require rescue medication or required less backup ibuprofen at 0-4, 4-8, and 8-12 hours after the onset of dysmenorrhea and starting treatment, as well as during the first 24 hours and for the duration of the menstrual flow, when compared with placebo TENS or ibuprofen-treated cycles (Tukey multiple comparison, P less than .01). Transcutaneous electrical nerve stimulation significantly delayed the need for ibuprofen by an average of 5.9 hours, compared with 0.7 hours when using ibuprofen alone (P less than .05, paired t test). Transcutaneous electrical nerve stimulation alone provided good to excellent subjective pain relief in 42.4% of subjects, compared with 3.2% with placebo TENS, and significantly reduced diarrhea, menstrual flow, clot formation, and fatigue compared with placebo TENS. Transcutaneous electrical nerve stimulation plus less ibuprofen provided pain relief equivalent to that obtained with ibuprofen alone (71 and 75% of the subjects, respectively). We conclude that TENS is a safe, effective, non-medication method for managing primary dysmenorrhea and that TENS plus ibuprofen was the best overall treatment, as indicated by pain relief.