Treatment drop-out is a common problem in the everyday practice of psychotherapy. In the cognitive-behavioral psychology literature, there are scant data on drop-out from therapy and the data available vary widely according to the definition of drop-out and the intensity of treatment. This study presents results obtained in the Behavioural Therapy Unit of the University of Barcelona. Of the 203 patients seen in the unit, 89 (43.8%) dropped out, mostly in the early stages of the intervention. The most common reasons for this were low motivation and/or dissatisfaction with the treatment or the therapist (46.7%), external difficulties (40%), and patients' feeling of improvement (13.3%). Patients who dropped out differed from those who continued; they more often presented affective or eating disorders or problems with impulse control. The observed drop-out rate is in line with figures reported for psychotherapy in general and by those studies which have considered cognitive-behavioral therapy in particular.