Fifty obsessive–compulsives were treated by behavioural therapy (self-exposure in vivo and response prevention) either with their partner directly involved in all aspects of treatment or without their partner. The two treatment formats were equally effective. Although a substantial number of obsessive–compulsives were found to have marital problems, behavioural treatment directed at the obsessive–compulsive disorder resulted in improvement irrespective of marital quality and partner involvement in the therapy. The effects of treatment led neither to a deterioration of the marriage nor to adjustment problems in the partner.