OBJECTIVE To determine the prevalence of systemic sclerosis (SSc) overlap syndrome and autoantibody profile in a large single-center cohort. METHODS SSc diagnoses, subsets, and autoantibody profiles were obtained from clinical records of patients attending the Centre for Rheumatology, Royal Free Hospital, between September 1999 and February 2007. RESULTS In total, 332 (20%) of 1700 patients with SSc had overlap syndrome. This comprised myositis (42.8%), rheumatoid arthritis (RA; 32%), Sjögren's syndrome (SS; 16.8%), and systemic lupus erythematosus (SLE; 8.4%). Antinuclear antibody was positive in 96.6% of patients. Anticentromere antibody (ACA) was exclusively present in limited cutaneous SSc (lcSSc) overlap cases (22%), and more common in SSc/SS overlap (44.7%), whereas no difference was found in the prevalence of Scl-70 autoantibody between lcSSc and diffuse cutaneous SSc overlap groups. U1RNP was more frequent in SSc/SLE (44%), while Ro antibody was more likely to be found in SSc/SS (29.8%). ACA was absent and anti-Scl-70 was infrequent in SSc/myositis; polymyositis-scleroderma antibody was more frequent in this group (33.1%). About 50% of patients had raised rheumatoid factor (RF), with no difference between overlap groups irrespective of RF titer. In contrast, anticyclic citrullinated peptide antibody was more frequent in patients with RA features. CONCLUSIONS About one-fifth of SSc cases had overlap features. There were distinct serological features that may predict specific clinical presentation and disease course.