Background. Since little is known about the long-term course and outcome of bulimia nervosa, the authors designed a 12-year prospective longitudinal study with five cross-sectional assessments based on a large sample of consecutively treated females with bulimia nervosa (purging type) (BN-P).

Method. One hundred and ninety-six females with BN-P were assessed (1) at the beginning of treatment, (2) at the end of treatment, (3) at 2-year follow-up, (4) at 6-year follow-up, and (5) at 12-year follow-up. In self-ratings as well as expert ratings based on interviews we assessed specific eating-disorder and general psychopathology.

Results. The general pattern of results over time showed substantial improvement during treatment, slight (in most cases non-significant) decline during the first two years after the end of treatment, and further improvement and stabilization until 12-year follow-up. At that point the majority of patients (70·1%) showed no major DSM-IV eating disorder, 13·2% had eating disorders not otherwise specified, 10·1% had BN-P and 2% had died. Very few had undergone transition to anorexia nervosa or binge-eating disorders. Logistic regression analyses showed that psychiatric co-morbidity was the best and most stable predictor for eating-disorder outcome at 2, 6 and 12 years.

Conclusions. Course and outcome of BN-P was generally more favourable than for anorexia nervosa.