This is a report on the household survey component of the study at Sault Ste. Marie, Ontario, exploring differences in medical care behavior between steelworker families in a prepaid group practice plan and those enrolled in an insurance company plan. Both were eligible for broad medical benefits and, through the provincial program, for unlimited hospital care. The survey was conducted from July 1967 through June 1968. Demographically similar, the study populations reported no significant differences in such indices as the incidence of acute illness, disability due to either, medical attendance in illness, and attitudes toward seeking medical care. Differences, confined to interactions with the health care system, included for group health plan members, concentration of services at their health center, with lesser use of hospital or other facilities in primary care; evidence of greater continuity of care in the insurance plan population as measured by care through usual physician, and substantially higher rates of hospitalization and surgery among the insurance plan participants. With the focus on hospitalization, comparisons are drawn as between certain data obtained through record analysis and those obtained through interviews, with a considerable degree of mutual validation of the two methods being revealed.