Health-related quality of life was examined in 49 patients with hepatitis C virus with no psychiatric history who received interferon (IFN)-α treatment. Quality of life was assessed at baseline, at 3-time points during IFN-α therapy and at 1-6 month follow-up, using SF-36. Hepatitis C virus patients showed poorer physical functioning and better social and mental functioning than a normal population. Significant decreases from baseline SF-36 scores were observed at an early phase of treatment. Six patients developed major depression during IFN-α treatment. At baseline, they had reported more bodily pain than patients who did not develop depression during treatment. Planned contrasts revealed that worsening in some dimensions of quality of life at 2 months was greater in depressed than in non-depressed patients. Results suggest that depressive symptoms should be accurately monitored during IFN-α therapy even in patients with no psychiatric history, especially if they present with bodily pain.