OBJECTIVE: This study provides a profile over time of the incremental health care costs of patients treated for depressive disorders, including attention to medical treatment costs, drug treatment costs, and incremental treatment costs (i.e., excess costs as compared to controls) for coexistent medical and psychiatric conditions. METHODS: Administrative claims data from seven large U.S. companies were used to identify 3,464 depressive disorder patients. A random sample of individuals who were not treated for depressive disorders served as controls. Incremental cost estimates were generated using a Tobit regression model including controls for age, gender, health plan, geographic location, and a number of medical conditions that tend to precede the onset of depressive disorders. RESULTS: We estimate that treated depressive disorder sufferers incur approximately $608 per month in incremental health care costs during their first depressive disorder episode. Of this total, 29.4 percent are due to medical treatment costs, 6.2 percent are due to drug treatment costs, and 64.4 percent are due to the incremental treatment costs of coexisting conditions. The costs of treating subsequent depressive disorder episodes decline. In addition, while the incremental costs of treating other medical and psychiatric conditions increase in the months prior to the first depression episode, these costs decrease in the months after a final depression episode. CONCLUSION: The health care costs incurred by treated depressive disorder sufferers in the U.S. are substantial. Depressive disorder patients experience a "run up" of costs prior to an episode diagnosis and a subsequent "run down" in costs after treatment for the condition. Future research will investigate the indirect costs (i.e., work loss and work cutback) associated with depressive disorders, as well as the family burden of depressive episodes using the same time profile approach developed here.