Data were obtained from 833 institutionalized drug users in southwest China. More than two-thirds of the sample reported frequent intravenous or intramuscular drug injection. Among injection drug users (IDUs), 78 percent shared needles. Compared to non-IDUs, IDUs who also shared needles had significantly higher rates of having multiple sexual partners and of never having used a condom. Findings suggest that IDUs in China are a population at high risk for HIV infection and underscore the urgency of preventing injection drug use and unprotected sexual practices among drug users in China. Injection drug use and unprotected sexual practices, in addition to endangering IDUs, also might facilitate the spread of HIV infection to other risk populations, e.g., the “transient population” of rural residents migrating to urban areas in search of jobs, and prostitutes. Tables, references