Objective: The present study (Shyness 7) has two aims: Firstly, to replicate an earlier trial showing that a self-guided Internet treatment for social phobia is efficacious, and secondly, to examine whether the addition of self-guided motivational enhancement strategies improves completion rates and clinical outcomes. Method: Randomized controlled trial (RCT) of self-guided Internet-based cognitive behavioural treatment (iCBT), or iCBT plus self-guided motivational enhancement strategies (iCBT+MS), was conducted. An intention-to-treat and last observation carried forward model was used for data analyses. The participants consisted of 108 volunteers with social phobia. The iCBT intervention consisted of two online lessons about symptoms and treatment of anxiety disorders and six lessons about management of social phobia (the Shyness programme) with complex automated reminders. The motivational intervention was based on traditional techniques including understanding and exploring ambivalence about change using a costbenefit analysis, developing and resolving discrepancy between values and symptoms, and enhancing self-efficacy for change. The main outcome measures were the Social Interaction Anxiety Scale and Social Phobia Scale. Results: More iCBT+MS group participants completed the eight lessons than iCBT group participants (75% versus 56%, respectively), but there were no between-group differences in outcome measures at post-treatment or at 3 month follow up. Large mean within-groups effect sizes (Cohen's d) for the two social phobia measures were found for both the iCBT and iCBT MS groups (1.1 and 0.95, respectively), which were sustained at 3 month follow up (1.06 and 1.07, respectively). Both iCBT and iCBT+MS group participants reported that the procedures were highly acceptable. Conclusions: Both self-guided versions of the Shyness programme were reliably efficacious, confirming that people with social phobia may significantly benefit from a highly structured self-guided intervention. The addition of motivational techniques increased completion rates but did not improve clinical outcomes or acceptability.