Objective: To compare adverse event data collected during administration of a triphasic norgestimate ethinyl estradiol (EE) containing oral contraceptive (OC) [ORTHO TRI-CYCLEN(R)] or placebo.Methods: Four-hundred fifty-two females between the ages of 15 and 49 years were enrolled in two multicenter, double-blind, randomized, placebo-controlled studies. These studies were conducted to evaluate the effectiveness of triphasic norgestimate/EE in the treatment of acne vulgaris (Redmond G, Olson W, Lippman J, et al. Norgestimate and ethinyl estradiol in the treatment of acne vulgaris: a randomized placebo-controlled trial. Obstet Gynecol 1997;89:X-X; Lucky A, Henderson T, Olson W, et al. The effectiveness of norgestimate and ethinyl estradiol in treating acne vulgaris. J Am Acad Dermatol, in press). Participants returned to the study centers monthly for evaluation. At each visit, interviews were conducted to elicit and record the occurrence of adverse events. Reports were derived by nondirected questioning.Results: The table below describes the number and percentage of subjects reporting the event during the 6-month period. Note that, over the range of percentages observed, the differences detectable with a power of 0.80 range from approximately 4% to 12%.Conclusion: Excellent tolerability for the triphasic norgestimate/EE OC is demonstrated by a low rate of side effects that did not differ in a statistically significant manner from placebo.