Past research has largely assumed that medical care use and expenditures for children are uniform across stages of family development. This study challenges that notion and investigates (a) differences in use of and expenditures for children's health services across stages of the family life cycle, and (b) the extent to which family characteristics affect medical care use and expenditures for children differently, depending on stage of the family life cycle. Data for the study are taken from the 1977 National Medical Care Expenditure Survey (NMCES). Stages of the family life cycle are identified on the basis of the age of the oldest child in the family. Family characteristics include family size, poverty status, number of parents, and mother's characteristics. The results show variation across stages of the family life cycle in terms of both children's mean number of physician visits and out-of-pocket health expenditures. Also, there were differences across certain stages in the effects of family size, single-parent status, mother's age, and mother's use of physician services on the number of children's physician visits. Mother's educational attainment and poverty status were found to have differential effects on out-of-pocket health care expenditures for children. The family is a social influence of considerable importance on the health and health behavior of children. Many have noted that the family plays a key role in the decision-making and therapeutic process at every stage of a child's illness (Litman, 1974). Medical sociologists and health services researchers have found that family characteristics play an important role in medical care use and expenditures for children. For example, family size shows a consistently strong relationship to use in that children from large families use fewer services than children from small families (Cafferata and Kasper, 1985; Kasper, 1975; Wolfe, 1980). Apparently, the time-cost of taking children to the doctor is higher in larger families, and children from small families benefit from more parental attention. Also, the presence of a spouse in a family appears to affect the health of children (Angel and Worobey, 1988) as well as their use of health services (Beck, 1974; Newacheck and Halfon, 1986a; Wilcox-Gok, 1983). Mothers are viewed as the gatekeepers to the health care system for children (Mechanic, 1964), and it can be expected that their characteristics and attitudes about health care play a prominent role in the decision to seek care for their children. Indeed, research has found that the employment status of mothers has an effect on the use of health services for their children (Cafferata and Kasper, 1985; Wolfe, 1980). Also, to the extent that employment increases a mother's NCHSR, 5600 Fisher's Lane, Room 18A55, Rockville, MD 20857.