Presented in this article are aggregate utilization and financial data from the four social health maintenance organization (S/HMO) demonstrations that were collected and analyzed as a part of the national evaluation of the S/HMO demonstration project conducted for the Health Care Financing Administration. The S/HMOs, in offering a $6,500 to $12,000 chronic care benefit in addition to the basic HMO benefit package, had higher start up costs and financial losses over the first 5 years than expected, and controlling costs continues to be a challenge to the sites and their sponsors.