Eighteen patients with acute leukemia were studied to evaluate their left ventricular systolic and diastolic function by M mode, two-dimensional and Doppler echocardiographic techniques. The study group was compared with another group of 18 patients of similar age with iron deficiency anemia. The latter group had a comparable heart rate and levels of Hb. There were no differences in systolic function, whereas the diastolic function was lower in patients with acute leukemia (E/A ratio = 1.1 ± 0.3 vs. 1.42 ± 0.5, p < 0.05). It is concluded that left ventricular diastolic dysfunction is more common in patients with acute leukemia and may be an indicator of restrictive cardiomyopathy.