The authors report the case of a 35 year old man with no known previous cardiac disease. One month after a tic bite causing diffuse abdominal erythema, he was admitted to hospital with fever, breathlessness and bradycardia. The electrocardiogramme showed first degree atrioventricular block with a sinoatrial block (SA = 200 ms, AH = 240 ms). Echocardiography eliminated the diagnosis of pericardial effusion. Thallium 201 myocardial scintigraphy was pathological and showed irregular global uptake suggesting cardiomyopathy. Gallium 67 scintigraphy showed increased uptake in the left ventricle. The evolution was uncomplicated with normalisation of clinical, ECG and radiological changes. Cardiac catheterisation and angiography eliminated ischaemic and primary cardiomyopathy. Control radionuclide investigations were normal at one month: there was no persistent abnormal Gallium uptake. The diagnosis of Lyme's syndrome was confirmed by positive serology with successive titres of 1/1024 and 1/2048 (significant at titres over 1/256). This unusual case illustrates: the risk of myocardial disease in Lyme's syndrome; the diagnostic value of Gallium 67 scintigraphy in acute myocarditis: Gallium seems to fix specifically on inflamed tissues, so distinguishing myocarditis from primary cardiomyopathies.