Although cardiac infiltration is common in advanced stage of acute leukaemia, it is not usually diagnosed at life and it is extremely rare for it to become pseudotumoral. A 25-years-old patient with an acute monoblastic leukaemia who had a leukaemic infiltration which affected the main part of the left ventricle at the time of diagnosis, is referred. The heart infiltration was detected by a two dimension echocardiography. In spite of a massive infiltration, heart failure was not present and the left ventricle's ejection fraction was 50%. Even though chemotherapy was administered, the patient died four days after diagnosis due to septic shock of respiratory origin. The most relevant autopsy finding was a widespread pseudotumoral infiltration of the left ventricle, the back side of the right ventricle and the interventricular wall. The pseudotumoral infiltration of the heart by acute leukaemia is uncommon and must be differentiated from granulocytic sarcoma. The usefulness of the different diagnostic procedures is discussed.