We report the case of a 40-year-old woman with a seasonal form of obsessive compulsive disorder (OCD) which was usually accompanied by obsessions and occurred only in autumn or winter. Frequently, the OCD symptomatology was accompanied by depression. After a 12-day treatment with full spectrum bright light (3000 lux; 2 hours a day between 9 and 11 am) without changing the long-term antidepressive medication (125 mg amitriptyline/day) there was a complete remission of OCD symptomatology, with no relapse during the next months.