Despite the growth of managed care, little is known about health plans' web sites. This paper reports on a review of the web sites of the 25 largest HMOs in the United States to identify whether their content included information deemed important by consumers: quality, price, provider network, personal health information, and customer service features. Findings show variation in the content of HMO web sites, with sites emphasizing customer service features, the provider network, and personal health information. Two-thirds of HMOs offer information on quality; however, pricing information is offered by only four plans. Implications for future differentiation of HMO web sites are discussed.