Of 39 diagnosed Seasonal Affective Disorder (SAD) patients who were interviewed 2–5 years after participation in a light therapy trial, 10 continued to have recurrent major depressive episodes in winter, and 17 manifested sub-syndromal SAD (2 patients also had recurrent brief depression, seasonal type). 8 patients had recovered, and 4 had shifted in symptomatology. Thus, over a number of years, the clinical diagnosis changed for the better in 64% of the patients, suggesting that SAD is not a prodromal form of a more chronic major affective disorder, and that light therapy (and perhaps also light-oriented behaviour) reduced the incidence and depth of subsequent depressive episodes. Further evidence for this was the large reduction in use of conventional antide-pressant drugs (from 17 to 1) during the follow-up period. Diagnosis of SAD was stable and reliable.