The purpose of this study was to investigate the effect of stress on the family due to the hospitalization of a family member for a serious chronic illness. The data were the health insurance claims of 3,591 families obtained from the largest U.S.A. insurer of federal employees. It was hypothesized that the nonhospitalized family members would have a stress-related increase in medical expenses for some period of time after the chronically ill person was hospitalized. Multiple regression analysis with adjustments for a number of covariates found increases in mean medical charges of $326 per person (p less than 0.01) (excluding the hospitalized person) in the 3 years following the hospitalization. This finding lends support to the theory that stress--in this case, hospitalization of one family member--affects the entire family system. No significant differences were found in medical charges between families who did and did not receive mental health treatment following the hospitalization.