Seasonal Affective Disorder (SAD) has been characterised by two or more depressive episodes in autumn or winter (with remission the following spring or summer), decreased energy, increased sleep, increased appetite, weight gain and carbohydrate craving. SAD patients were identified in a Swiss-German population; 22 participated in a light-therapy protocol (1 week bright white light 2,500 lux or dim yellow light 250 lux, from 06-08 h and 18-20 h). Both observer and self-ratings indicated a significant diminution of depressive symptoms with both lights. One week after withdrawal from yellow light, depression ratings relapsed to previous values; remission lasted longer after bright white light. Global VAS self-rating scales for "mood" and "well-being" however, and the Hamilton scale for atypical SAD symptoms, differentiated clearly between bright and dim light: only bright light showed an improvement that persisted after withdrawal. These results suggest that even though a placebo effect cannot be excluded, 4 h explicit light exposure/day may not be a negligible quantity. Light treatment promises to be a useful non-pharmacological intervention in certain forms of depressive illness.