Two-dimensional echocardiography is the reference technique for the diagnosis of left ventricular thrombi. However, it has some limitations due to poor imaging of the apex; location of many thrombi. Apical resolution improvement is possible using a 5 MHz ultrasonic transducer, which may identify 3.5MHz ultrasonic transducer false positive results. In a series of 53 patients with left ventricular dysfunction, we detected 11 thrombi. Using the 5MHz ultrasonic transducer as a reference the sensitivity of the 3.5MHz ultrasonic transducer was 100%, and much greater than that of the 2.5MHz ultrasonic transducer (55%), which was associated with 4 false positive results. The increased sensitivity associated with transducers of higher frequency was however limited by the echogenicity of patients, all the more since we used a medium instead of a short focalisation. Due to its therapeutic consequences, the detection of left ventricular thrombi must be enhanced using 5 MHz ultrasonic transducer, all the more in echogenic patients.