Marketing the Social/Health Maintenance Organization (S/HMO) relative to HMOs and fee-for-service health insurance is a complex undertaking. Awareness of the plans is relatively high among joiners and nonjoiners, as is awareness of the relative price and benefits of these competing options. Local market competition and out-of-pocket costs appear to be major factors in selection. Study subjects include a probability sample of S/HMO members in 1986 and probability samples of elderly Medicare beneficiaries who had enrolled in HMOs or were fee-for-service recipients within the demonstration communities.