Internet-based self-help for social phobia with minimal therapist support via email have shown efficacy in several controlled trials by independent research teams. The role and necessity of therapist guidance is, however, still largely unclear. The present study compared the benefits of a 10-week web-based unguided self-help treatment for social phobia with the same intervention complemented with minimal, although weekly, therapist support via email. Further, a third treatment arm was included, in which the level of support was flexibly stepped up, from no support to email or telephone contact, on demand of the participants. Eighty-one individuals meeting diagnostic criteria for social phobia were randomly assigned to one of the three conditions. Results showed significant symptom reductions in all three treatment groups with large effect sizes for primary social phobia measures (Cohen's d = 1.47) and for secondary outcome measures (d = 1.16). No substantial and significant between-groups effects were found on any of the measures (Cohen's d = .00−.36). Moreover, no difference between the three conditions was found regarding diagnosis-free status, clinically significant change, dropout rates, or adherence measures such as sessions or exercises completed.