This article examines the information technology functions, staffing and cost, services provided, and advanced technologies among health maintenance organizations (HMOs) using a national sample of HMOs from mid-1995. HMOs have a well-developed capability to use data from administrative functions, such as claims processing. Nationally affiliated HMOs and HMOs in markets with greater HMO penetration support more IT functions. Relatively little work has been completed integrating clinical with administrative systems.