The Consumer Assessment of Health Plans Study (CAHPS) is intended to develop an integrated, standardized set of surveys to collect valid information about health plan performance from consumers. This article reports psychometric results for the CAHPS 1.0 survey items in individuals with Medicaid or private health insurance coverage. Reliability estimates for CAHPS 1.0 measures were estimated in a sample of 5,878 persons on Medicaid and 11,393 persons with private health insurance. Correlation of CAHPS global rating of health plans with willingness to recommend the plan and intention to re-enroll were estimated in 313 persons on Medicaid. CAHPS measures appeared to have good reliability, particularly at the health plan level. Global health plan rating was significantly correlated with consumers' willingness to recommend the plan to family and friends and to their intention to re-enroll in the plan. The CAHPS 1.0 survey instrument appears to have excellent psychometric properties.