Objective: We conducted a comprehensive review of the English language literature on the comorbidity of anxiety symptoms/disorders in schizophrenia spectrum disorders (SSDs) in order to determine: their prevalence rates in clinical and non-clinical populations, the temporal relationship of anxiety comorbidity to SSDs, and the effect of comorbidity on outcome. Method: Medline and PsychInfo databases were searched, from 1966 to September 2004 and 1887 to September 2004 respectively. Results: Overall lifetime prevalence rates for any anxiety disorder ranged from 30% to 85% with most studies showing rates higher than in the general population. In more than 50% of patients, the anxiety disorder preceded the onset of psychosis. Patients with comorbid panic symptoms were more frequent service users, had additional comorbidities and were more likely to be suicidal. Comorbid obsessive-compulsive symptoms (OCS) tended to be associated with poorer social functioning, worse cognitive impairment and motor symptoms. Conclusions: There is a clear link between SSDs and anxiety disorders though its nature remains unclear. This has important implications for psychiatric nosology, aetiology and treatment.