How do large public employers go about purchasing health plans? What effect do those practices have on premiums? This project was designed to study large public employers' health plan purchasing practices as prototypes of health insurance purchase cooperatives (HIPCs). The researchers inventoried current health plan purchasing practices and estimate the effect of those practices on premiums. The study gathered data regarding: (1) employers' decisions to offer multiple plans; (2) standardization of benefit packages among health plans; (3) information provided to employees during open enrollment periods; (4) risk adjustments among multiple plans; and (5) methods for determining employer premium contributions. The objective of this research was to provide information which will assist policymakers as they design and implement HIPCs.