Health insurance claims of families covered by Aetna's Federal Employees Health Benefit Program from 1980 through 1983 were analyzed to determine if any changes in total health care utilization and costs were associated with the initiation of mental health treatment. A total of 26,915 families in which at least one member received mental health treatment were compared with a randomly selected group of 16,468 families in which no member had received mental health treatment. Total health care costs for those receiving mental health treatment were significantly higher than costs for the comparison group. However, those costs dropped significantly after initiation of mental health treatment and continued to decline over the study period. The biggest declines occurred among persons age 45 and older, a finding that may have important policy considerations.