Not enough is known about which patients suffering from major depressive disorder benefit from antidepressant drug treatment. Individual temperament is relatively stable over a person's lifespan and is thought to be largely biologically predefined. We assessed how temperament profiles are related to depression and predict the efficacy of antidepressant treatment. METHODS: We recruited one hundred Finnish outpatients (aged 19 to 72) suffering from major depressive disorder, of whom 86 completed the 6-week study. We assessed their temperament features with the Temperament and Character Inventory and used cluster analysis to determine the patient's temperament profile. We also categorized the patients according to the vegetative symptoms of major depressive disorder. RESULTS: There was an association between skewed temperament profile and severity of major depressive disorder, but the temperament profiles alone did not predict antidepressant treatment response. Those with higher baseline vegetative symptoms score had modest treatment response. Our model with baseline Montgomery Åsberg Depression Rating Scale (MADRS) vegetative symptoms, age and temperament clusters as explanatory variables explained 20% of the variance in the endpoint MADRS scores. CONCLUSION: The temperament clusters were associated both with severity of depression and antidepressive treatment response of depression. The effect of the temperament profile alone was modest but, combined with vegetative symptoms of depression, their explanatory power was more marked suggesting that there could be an association of these two in the biological basis of MDD.