This paper describes a small set of successful school-based clinics (SBCs) that provide primary health care services for the underserved and identifies factors contributing to their success. Six sites were selected on the basis of three general criteria: (1) direct involvement between the SBC and a federally-funded community health center (CHC); (2) wide geographic distribution with urban/rural representation; and (3) a demonstrated measure of success in terms of substantial student enrollment. A visit was made to each clinic and interviews were conducted with the clinic director, key staff, a CHC manager, and student-users of the clinic. Based on the data collected, a case study was written for each site, providing information on the following SBC topics: geographic characteristics; characteristics of the student population; brief history and mission; management and staffing; space and facilities; outreach and marketing efforts; services offered; costs and financing; impact of services; ongoing concerns and problems; and keys to success. (Contains 28 exhibits and 26 references.) (LL)