Family day care--child day care provided in a private home other than the child's own--includes more children than any other mode of day care in the United States. Day care homes have traditionally cared for a large proportion of younger children, particularly infants and toddlers, who are most likely to contract and spread infectious diseases. The majority of homes are run on an informal basis and are neither licensed nor registered; a small minority of homes are regulated or operated under sponsorship of an umbrella agency. Homes generally have fewer children than do day care centers, and when children of different ages are cared for, they usually mix freely. Care givers in homes, especially in those that are not registered, are unlikely to have had child care-specific training. Parent fees in homes and centers appear roughly comparable, with fees in nonregulated homes generally lower than those in regulated or sponsored homes. It is difficult to compare the actual costs of child care in these settings. Results of the small number of studies comparing the occurrence of infectious diseases among children in day care centers, day care homes, and at home suggest that the rates of some infections may be lower in day care homes than in centers; this effect may vary by age and infections. Because of the large population of young ages of children involved in family day care, additional study and recommendations regarding infections in this setting are needed.