Fifty-two cases of toxic-shock syndrome that occurred in January 1, 1976 through August 31, 1980, were reported to the Utah State Health Department between February 1 and August 31, 1980. The annual attack rate for Utah based on a six-month surveillance period was 14.4 per 100,000 women ages 12-49 years. All cases were in women who had onset of illness within two days of menses. Potential risk factors were investigated with a case-control study utilizing 29 women hospitalized with toxic-shock syndrome and 91 neighborhood female controls. Nine of the 29 (31%) women reported recurrences of similar illness. Use of tampons (p = 0.012) and use of a single brand of tampon-Rely-during the month of illness (p less than 0.005, RR =6.11) were associated with a significantly increased risk of acquiring toxic-shock syndrome. More controls were sexually active than women who had toxic-shock syndrome (p less than 0.05, RR - 0.277). This epidemiologic investigation of toxic-shock syndrome in menstrual-age women has identified tampons generally and a single brand specifically as significant risk factors in acquiring toxic-shock syndrome.