In this study, the effect of bright white light (2500 lux) and dim light (50 lux) were assessed in 30 patients with non-seasonal major depressive disorder randomly assigned to either procedure. Patients met RDC for major depressive disorder and ICD-9 criteria (296.1 and 296.3). During a 7-day period, the patients were exposed to bright white light (2500 lux) or dim light (50 lux) from 7.00 to 9.00 h daily. The severity of depression was assessed with observer scales (AMDP system, Hamilton depression scale, CGI) and through self-evaluation by self-rating scales (depression scale and list of complaints by von Zerssen). No difference was noted between bright light therapy and dim light, though a significant reduction of depressive symptomatology was observed for all patients during the study. These findings are discussed from a clinical point of view.