This study investigated the psychometric properties of the Social Phobia Inventory [SPIN; Connor, K. M., Davidson, J. R. T., Churchill, L. E., Sherwood, A., Foa, E., Wesler, R.H., 2000. Psychometric properties of the Social Phobia Inventory (SPIN). British Journal of Psychiatry, 176, 379-386], a measure of severity in social phobia (social anxiety disorder). Participants included 132 participants with social phobia, 57 participants with panic disorder and agoraphobia (PDA), and 62 participants with obsessive-compulsive disorder (OCD). Confirming findings from an initial validation study, the SPIN was found to have excellent internal consistency and good test-retest reliability. It also distinguished well between those with social phobia and those with either PDA or OCD. Good convergent and discriminant validity were established by examining correlations with other conceptually related and unrelated scales. Finally, the SPIN was sensitive to changes in social phobia severity following cognitive behavioral group treatment. In conclusion, the SPIN is both reliable and valid for the measurement of social phobia severity and outcome following psychological treatment.