Exposure to HIV in the workplace is a major concern for health care workers. The greatest risk for bloodborne pathogen transmission is associated with percutaneous injuries involving hollow-bore needles contaminated with patient blood. Limited data are available about how many sharps injuries (SIs) and needlesticks (NSs) occur in the United States, with estimates ranging from 100,000 to 1 million injuries per year. We conducted a survey of 100 infection control practitioners located at randomly selected U.S. hospitals to assess the number of SIs or NSs occurring during 1990; 65 (65%) responded. The mean number of NS/SIs reported was 45, with a mean of 1.1 known HIV-related NS/SIs. The underreporting rate was estimated to be 18.5%. Assuming that the hospitals provided exact numbers of injuries and were representative of the approximately 5,100 U.S. hospitals, then about 252,000 NS/SIs were reported in U.S. hospitals in 1990 (95% CI = 193,000-312,000). If the under-reporting rate was 33% to 66%, then the point estimate for the total number of NS/SIs ranges from 378,000 to 756,000. Similar extrapolation involving the reported number of NS/SIs contaminated with blood from an HIV-infected patient yields an estimate of 5,610 exposures in 1990 (95% CI = 1,300-8,300). The number of U.S. hospital workers sustaining NS/SIs with potential exposure to HIV appears to be considerable. Efforts to reduce the risk of bloodborne pathogen transmission from NS/SIs are warranted.