The authors analyzed switches between prepaid and fee-for-service health care plans among depressed outpatients in the longitudinal part of the Medical Outcomes Study. Patients of mental health specialists in fee-for-service plans had the lowest adjusted rate of plan switching (8.1%), compared to fee-for-service general medical patients (13.5%) and prepaid patients of both types of providers (10.1% to 11.7%). Although there were no substantial differences in initial sickness by payment system among enrolled patients, differing switching rates by provider specialty and payment system indicated biased selection over time. In addition, the authors found that married, nonwhite, and wealthier individuals were significantly more likely to leave fee-for-service than prepaid care plans. The authors analyzed whether system switching had an effect on patient satisfaction and outcomes. None of the results were highly significant, but the power of the data to analyze this issue was limited. Nevertheless, it appears that patients switching from prepaid to fee-for-service may be at risk for poorer functioning outcomes, although there was no similar effect on mental health status.