In January 1980, the Minnesota Department of Health began a surveillance system for toxic-shock syndrome (TSS) with both epidemiologically defined active -and passive components. As of June 30, 1981, 197 confirmed cases of TSS, 15070 of all nationally reported cases, have been in Minnesota residents. The onset in 61 of the cases was before 1980; these cases were retrospectively recognized and reported. Of the 136 cases reported between January 1980 and June 1981, 114 (83.8070) cases were tampon-associated. During the 18 months of active surveillance, there was no difference (P> 0.2) in the quarterly distribution of total or tampon-associated TSS cases. The onset of illness in 55 tampon-associated cases was during the nine months of surveillance in which Rely" tampons (Procter and Gamble, Cincinnati, Ohio) were on the market, whereas the onset in 59 tampon-associated cases was during the nine months following their removal from the market.