Osteoarticular infections (osteomyelitis and septic arthritis) were studied in 693 episodes of infective endocarditis (IE) presenting to St. Thomas' Hospital (STH) between 1969 and 2002. The incidence of osteoarticular infections (OAI) was 4.3% (30/693). In intravenous drug users (IVDU), the incidence of OAI was 17.6% (9/51). 22 (73%) were clinically definite by the modified Duke criteria and 8 (27%) were probable. The respective figures using the St. Thomas' modified criteria were 83% and 17%. Blood cultures were positive in 93% (27/29). Only Gram-positive organisms were isolated. Infection mainly involved the vertebrae and large joints. Culture of joint fluid or bone was positive in 82% of cases (14/17). Over half the patients who developed OAI had major embolic complications of IE and the overall mortality was 33%. Bivariate analysis of risk factors for OAI in endocarditis showed statistical significance for S. aureus bacteraemia (OR 4.2, 1.9-9.3), IVDU (OR 6.3, 2.5-15.7), tricuspid valve involvement (OR 4.2, 1.8-9.6), pulmonary emboli (OR 3.9, 1.2-11.8) and emboli to the CNS (3.9, 1.5-9.9); on multivariate analysis, however, only S. aureus bacteraemia (OR 3.9, CI 2.5-5.9) and IVDU ( OR 3.2, CI 2.0-5.2) were associated with OAI in IE.