The incidence of bacteraemia during transoesophageal echocardiography (TEE) was evaluated in a prospective study of 82 consecutive patients. Three series of blood cultures were carried out for each patient: from group 1 (n = 44), prior to the examination, at the end of the examination and 15 min afterwards. For group 2 (n = 38), blood cultures were performed prior to the examination, 10 min after the start and immediately after the end. A single positive blood culture was detected in two patients. For the first patient, blood culture at the end of the examination demonstrated Corynebacteria, and for the second, Staphylococcus epidermidis was identified on cultures taken during the examination. During the first 24 h, a transient subfebrile temperature was recorded in 15% of the patients, including the patient with the Corynebacteria-positive blood culture. By mid-term (6 months) no patient had developed endocarditis. Our findings suggest that antibiotic prophylaxis during TEE is not warranted.