The long-term association between social support and symptomatology is studied. Social support variables were: experienced understanding, satisfaction, number of contacts, social support seeking and severity of interpersonal conflicts. Data were collected at the start of a short-term behavioural therapy (T1) and 6 (T2) and 18 months later (T3). In addition, a comparison is made between patients who had finished their therapy by the second measurement and those who were by that time still in therapy. A fine-grained analysis demonstrated that of all social support variables interpersonal problems were most strongly related to symptomatology, in particular to interpersonal sensitivity. The tendency to seek social support becomes associated with well-being in the long term. The best predictors of symptomatology at T3 were the initial severity of symptomatology, the change in severity of symptomatology between T1 and T2 and the severity of symptomatology at T2. The social support variables did not have any prognostic significance. All social support variables retained their high temporal stability. Results are translated into practical suggestions that might help maximize gains of short-term behavioural therapy within primary mental health care.