The objective of this study was to model the cost-effectiveness of escitalopram in comparison with generic citalopram and venlafaxine in primary care treatment of major depressive disorder (baseline scores 22-40 on the Montgomery-Asberg Depression Rating Scale, MADRS) in Denmark. A three-path decision analytic model with a 6-month horizon was used. All patients started at the primary care path and were referred to outpatient or inpatient secondary care in the case of insufficient response to treatment. Model inputs included drug-specific probabilities derived from systematic literature review, ad-hoc survey and expert opinion. Main outcome measures were remission defined as MADRS < or = 12 and treatment costs. Analyses were conducted from healthcare system and societal perspectives. The human capital approach was used to estimate societal cost of lost productivity. Costs were reported in 2004 DDK. The expected overall 6-month remission rate was higher for escitalopram (64.1%) than citalopram (58.9%). From both perspectives, the total expected cost per successfully treated patient was lower for escitalopram (DKK 22,323 healthcare, DKK 72,399 societal) than for citalopram (DKK 25,778 healthcare, DKK 87,786 societal). Remission rates and costs were similar for escitalopram and venlafaxine. Robustness of the findings was verified in multivariate sensitivity analyses. For patients in primary care, escitalopram appears to be a cost-effective alternative to (generic) citalopram, with greater clinical benefit and cost-savings, and similar in cost-effectiveness to venlafaxine.