To determine the prevalence of family care, we measured the extent to which a subset of 732 families, from those enrolled in the Rand Health Insurance Experiment, perceive and use a single primary care physician. Although only 16.7% of these families had all members with a majority of their visits to the same physician, 45.4% identified a single primary care physician for all family members. (For older couples, this percentage reached 73.5%). An intermediate proportion of families had visits by all family members to a single physician. Children received less family care, but as families matured, family care increased for both children and parents. Our results suggest an inverse relationship between family care and education level. The availability of general-family practitioners, family income, insurance coverage, and population size were not significant determinants of family care. We conclude that family members share the perception of having a single "family physician," which is reflected in their patterns of utilization.