Recognition of social anxiety disorder (social phobia) as a common and disabling condition has led to new advances in its pharmacotherapy. Limitations with selective serotonin reuptake inhibitors (side-effects) and behaviour therapy (scarcity of trained therapists), coupled with the tendency for patients with the disorder to self-medicate with alternative treatments, have led to the interest in Hypericum perforatum (St John’s wort) for this disorder. Although the literature is mixed, H. perforatum has demonstrated efficacy in several double-blind depression trials and some open-label studies with anxiety disorders. There is pharmacokinetic evidence for the serotonergic, domaminergic and gamma-amino butyric acid minergic activity of hypericum, all of which are implicated in social anxiety disorder. This study was designed to generate pilot data to examine the potential efficacy of H. perforatum in generalised social anxiety disorder. Forty subjects were randomised to 12 weeks of treatment with a flexible dose (600–1800 mg) of H. perforatum (n = 20) or placebo (n = 20). Subjects with comorbid depression (clinician HAMD > 16) were excluded. Results found no significant difference between mean change on the Liebowitz Social Anxiety Scale with H. perforatum (11.4) and placebo (13.2), P = 0.27, effect size = −0.09. Post hoc analyses found larger effects sizes associated with increased baseline severity, omitting patients with variable scores (± 30%) during the first week and use of self-report HAMD scores for exclusion.