Background: The efficacy of cognitive behaviour therapy (CBT) in social phobia has been demonstrated in several controlled trials and meta-analyses, but no comparison of CBT with supportive therapy (ST) can be found in the literature. Method: The aim of the trial was to study the effectiveness of CBT versus ST carried out ‘as usual’. Sixty-seven DSM-4 social phobic patients (89% generalized subtype, most with avoidant personality) were randomly allocated into two groups. Group 1 (CBT) received 8 1-hour sessions of individual cognitive therapy (CT) for 6 weeks, followed by 6 2-hour sessions of social skills training (SST) in group weekly. Group 2 received ST for 12 weeks (6 half-hour sessions), then the patients were switched to CBT. All patients agreed not to take any medication during the whole trial. In group 1, 29 patients reached week 6, 27 reached week 12, and 24 weeks 36 and 60 (endpoint). In group 2, 29 patients reached week 6, 28 reached weeks 12 and 18, 26 week 24, and 23 reached weeks 48 and 72 (endpoint). Results: At week 6, after CT, group 1 was better than group 2 on the main social phobia measure. At week 12, after SST, group 1 was better than group 2 on most of the measures and demonstrated a significantly higher rate of responders. This finding was replicated after switching group 2 to CBT. Sustained improvement was observed in both groups at follow-up. Compliance with abstinence from medication increased over time. Conclusions: CBT was more effective than ST and demonstrated long-lasting effects. This may suggest that social phobia management requires more than a simple and inexpensive psychological intervention.