Gray's behavioural inhibition and behavioural activation (BIS/BAS) neural systems model has led to research on approach and withdrawal as the two most fundamental dimensions of affective behaviour, and their role in psychopathology. Although Gray proposed the BIS as the neurological basis of anxiety, there are no reports examining approach and withdrawal predispositions in social anxiety disorder. Here we report approach and withdrawal predispositions in a group of 23 non-medicated individuals with social anxiety disorder (SAD) without co-morbid depression and in 48 normal controls. Results show increased BIS and decreased BAS fun-seeking in SAD subjects thereby underscoring Gray's dimensional model.