BACKGROUND The present study used cluster analysis procedures to identify empirically subgroups of patients with social phobia in a large clinical sample. METHODS The Liebowitz Social Anxiety Scale (LSAS) was administered to 382 patients from several studies of the treatment of social phobia. LSAS fear ratings were summed into four subscale scores (social interaction, public speaking, observation by others, eating and drinking in public) based on a previous factor analytical study of the LSAS. In order to produce a stable and robust solution, these factor scores were submitted to a two-stage clustering procedure consisting of an agglomerative-hierarchical clustering method followed by an iterative non-hierarchical clustering method. RESULTS Three patient subgroups were identified based on their pattern of feared social situations on the LSAS. These groups were labelled: (1) pervasive social anxiety; (2) moderate social interaction anxiety; and (3) dominant public speaking anxiety. Clusters differed significantly on age and age of social phobia onset, as well as on measures of social anxiety, general anxiety and depressive symptomatology. Clusters also differed in the percentage of assigned patients who met criteria for the generalized subtype of social phobia and avoidant personality disorder. CONCLUSIONS The results provide empirical support for the existence of three subgroups in a clinical sample of individuals with social phobia and contribute to the growing evidence for the heterogeneity of social phobia. Further study of the conceptual, clinical and aetiological significance of these subgroups is needed.