To ascertain the risk factors associated with toxic shock syndrome in Oregon a retrospective questionnaire was given to 18 patients (cases) and to two sets of age- and sex-matched controls. One set of controls consisted of friends (friend-controls) chosen by each patient. The second set of controls was selected from women attending a family planning clinic (clinic-controls). Patients were more likely to have used Rely (Procter & Gamble) tampons than friend-controls who were tampon users (p less than 0.05). There was no significant difference between cases and friend-controls with respect to birth control methods. There were no significant differences between cases and controls for history of sexually transmitted diseases or vaginal infection, frequently of intercourse, intercourse during menstruation, or frequency of tampon change.