Comparative outcome studies of generalised anxiety disorder suggest that psychological therapy is a potentially valuable alternative to anxiolytic medication. However, on average psychological therapy results in modest improvements in symptoms, with about 50% of patients achieving normal functioning. Limited follow-up data indicate that these changes are maintained over six months. Cognitive therapy appears to be most effective, although comparisons with other therapies are limited and non-specific factors are clearly important. There is also evidence of considerable variability in outcome between studies, with the best results obtained with patients who are free of anxiolytic medication and recruited directly from primary care or other non-psychiatric settings. The effects on outcome of patient characteristics known to be associated with more severe illness and complexity of clinical presentation have yet to be explored. A balanced appraisal of the value of psychological therapy with this common condition requires a fuller description of sample characteristics and more systematic investigation of the clinical significance of treatment effects over the long term.