OBJECTIVES To determine the prevalence of hospital web sites, the types of information provided within these sites, and the relationship of information to institutional characteristics. DESIGN Online search of hospital web sites over a 6-week period in late 1999. Web sites were abstracted for content. Bivariate comparisons were made of hospital profit status and ownership or operation by a multihospital network. PARTICIPANTS California acute care hospitals and their web sites. MAIN OUTCOME MEASURES Operation of web sites and web site content. RESULTS Among 390 California hospitals, 242 (62%) had easily identifiable web sites, 59 (15%) had no web sites, and 89 (23%) had sites identified only after telephone follow-up. Hospitals without sites were more likely not-for-profit, small, rural, or unaffiliated. The presentation of information was inconsistent, although most (93%) provided basic contact information. Many hospitals provided health content information (70%) or mentioned health classes (65%), but few guaranteed the quality of this information. Patient care features (online health profiles, risk identification, e-mail) were infrequent (13%) and rudimentary. Product advertising was frequent (54%) but was often nonhealth-related and unobtrusive. Of the 36% of hospitals that reported information on quality, few of the designated measures were valid and reliable measures of quality. Overall, 21% of hospitals reported accreditation (Joint Commission on Accreditation of Healthcare Organizations) status, and for-profit hospital web sites were more likely to report this accreditation. CONCLUSION [corrected] Consumers should be aware of current limitations in using information on hospital web sites. In the future, hospitals may better realize the potential of web sites for the delivery of health care information and patient care.