Based on data from the National Health Interview Survey Mental Health Supplement, 1989 (NCHS, 1991), this article compares health outcomes for respondents living with someone who is mentally ill (N = 776) with a randomly selected subsample of respondents not living with someone identified as mentally ill (N = 716). When other predictors of health are controlled, sharing a household with a mentally ill person is associated with poorer self-reported physical health, increased risk of reporting some activity limitation, and increased service utilization-both greater risk of hospitalization or visiting a physician, and a greater number of days hospitalized and number of physician visits among those utilizing these services. The severity and duration of mental illness have little effect across health outcome measures. Impaired health and increased utilization of medical care among persons living with someone who is mentally ill suggest hidden costs to individuals, to families of the mentally ill, and to the service system.