The purpose of this study was to evaluate whether 1-year total healthcare expenditures differed between patients who initiated therapy on a tricyclic antidepressant (TCA) or a selective serotonin reuptake inhibitor (SSRI) after controlling for initial antidepressant selection and antidepressant use pattern. A retrospective claims database covering a privately insured population in the US was used. Patients who initiated therapy in the outpatient setting (primary care or psychiatrist) were considered. Two-stage sample selection models were estimated that included controls for initial antidepressant selection and use pattern. The analyses indicated that: (i) self-selection due to initial antidepressant selection was a statistically significant determinant of expenditures for patients who initiated therapy on a TCA but not an SSRI; (ii) after controlling for initial antidepressant selection, antidepressant use pattern was a statistically significant and positive determinant of expenditures for both TCA and SSRI patients; and (iii) after controlling for initial antidepressant selection and use pattern, 1-year total direct healthcare expenditures were significantly lower for patients who initiated therapy on an SSRI than for patients who initiated therapy on a TCA.