This study evaluated a 9-week Internet-based self-help program for people suffering from social phobia. After confirming the diagnosis with a structured clinical interview for the "DSM-IV" (SCID) by telephone, 26 participants were treated with a multimodal treatment package based on cognitive behavioural therapy plus weekly therapist contact via email. Results were analysed on an intention-to-treat basis. There were no differences between the two pretreatment assessment points. However, from the pretest to posttest assessment points, treated participants improved significantly on all measured dimensions (social anxiety, general anxiety, depression levels, and quality of life). The overall within-group effect size measured with Cohen's d was d = 0.88. Treatment gains were maintained or improved at the 6-month follow-up (Cohen's d = 1.31). The results of this study support the continued use and development of Internet-distributed self-help programs for people diagnosed with social phobia. (Contains 3 tables.)