The Wisconsin Division of Health conducted a review of discharge coding for 142 (97%) of the state's general care hospitals for the period 1980-1983 to evaluate the use of International Classification of Diseases codes for toxic shock syndrome and to estimate completeness of reporting of recognized hospitalized cases of the syndrome to the Division of Health. Hospital use of code 040.89 (other bacterial diseases-other) recommended for toxic shock syndrome by the National Center for Health Statistics in January 1981 increased from 23% of Wisconsin hospitals in 1980 to 92% in 1983. The sensitivity of this code for toxic shock syndrome increased from 54% to 85% from 1981 to 1983; study population specificity was stable at approximately 95%, and the predictive value was 65% in 1981 and 70% in 1983. The use of codes 785.50 (shock, unspecified) and 785.59 (nontraumatic shock-other) frequently assigned to toxic shock syndrome was also assessed; all measures of their utility decreased in proportion to the increasing use of 040.89. The coding review identified 20 previously unreported cases of toxic shock syndrome; the 10 confirmed and 10 probable cases represent 4% and 21% of the state's 223 confirmed and 47 probable cases with onsets in 1980-1983. Results indicate that a National Center for Health Statistics coding recommendation for a disease of emerging significance can result in relatively uniform coding of the illness, which can provide a tool for case finding and surveillance evaluation for hospitalized cases.