The incidence of depression in acne patients using isotretinoin was assessed in 100 patients with moderate and nodulocystic acne. All patients received 0.75-1.00 mg/kg/day of isotretinoin for 20-28 weeks after acne was assessed. All patients' acne lesions were improved at the end of the treatment period. Psychological state was evaluated at baseline, at Month 3, and Month 6 by a psychiatrist using a Turkish version of the Hamilton Depression Rating Scale. Only one patient's score increased to the clinical level of depression at Month 3 of treatment and declined to subclinical levels at Month 6. Although Hamilton scores increased at Month 3 over baseline scores, except for one patient, others' scores remained below the subclinical level for depression. At the end of Month 6, the mean score decreased below that at Month 3. These changes in means might be related to the onset of clinical effect of isotretinoin.