A retrospective study was undertaken to analyse the risk factors for systemic emboli in infective endocarditis. Patients (n = 80; 70% males; mean age 65 years; range 20-91 years) with infective endocarditis, as defined by the Duke criteria and diagnosed using transoesophageal echocardiography during the period January 1995 to March 2001, were included. The average time between the start of the illness and the beginning of antibiotic treatment was 55 days (range 0-405 days). The pathogens identified were streptococci (n = 47), staphylococci (n = 11), enterococci (n = 9), and others (n = 4). In nine cases, blood cultures were sterile. Thirty patients with at least one embolic episode were compared with 50 control patients. According to univariate analysis, the main risk factor for systemic emboli was the size of the vegetation (12.4 mm vs. 7.8 mm; p = 0.0005). The risk of emboli was 57% when the vegetation measured > 10 mm and only 22% when it was < 10 mm (p = 0.003). The mobility of the vegetation was also a risk factor: 48% if the vegetation was mobile; and 9% if fixed (p = 0.003). Sex, age, pathogen, antibiotic treatment, type of valve and the number and position of the vegetations were not found to be risk factors. With multivariate analysis, only mobility was identified as a risk factor. Overall, mobile vegetations > 10 mm in size were associated with an increased risk of embolic episodes in infective endocarditis.