Background. Generalized anxiety disorder is a common condition of excessive worry and tension which tends to run a chronic course associated with significant psychiatric and medical problems. Cognitive behaviour therapy (CBT) has been shown to be of clinical value in about 50%of cases with treatment gains maintained over follow-up periods ranging from 6 to 12 months. The potential value of CBT over the longer term has not been subject to rigorous investigation. Method. Results are reported of 8–14 year follow-up of two randomized controlled trials of cognitive- behaviour therapy for generalized anxiety disorder employing structured interview with an assessor blind to initial treatment condition. Comparison groups included medication and placebo in one study based in primary care, and analytical psychotherapy in the other based in secondary care. Follow-up samples (30% and 55% of trial entrants) were broadly representative of the original cohorts. Results. Overall, 50% of participants were markedly improved of whom 30–40% were recovered (i.e. free of symptoms). Outcome was significantly worse for the study based in secondary care in which the clinical presentation of participants was more complex and severe. For a minority (30–40%), mainly from the secondary care study, outcome was poor. Treatment with CBT was associated with significantly lower overall severity of symptomatology and less interim treatment, in comparison with non-CBT conditions, but there was no evidence that CBT influenced diagnostic status, probability of recovery or patient perceptions of overall improvement. Conclusions. Both CBT and the complexity and severity of presenting problems appear to influence the long-term outcome of GAD.