In response to an expressed need for comprehensive data on health sciences libraries in hospitals, the American Hospital Association (AHA) conducted a survey of all U.S. registered hospitals in 1990. The response rate was 57%. Results showed that 2,167 hospitals (31.6% of all U.S. registered hospitals) had on-site libraries that met four definitional criteria. Survey results also indicated that hospitals use diverse resources and approaches to provide information services to a wide array of health care providers and consumers. These baseline data, combined with an assessment of key environmental factors affecting hospitals, can provide guidance to hospital libraries as they face the challenges of the 1990s. The AHA has added the health sciences library to services tracked in its annual survey of hospitals; additional research opportunities in this area remain.