Patterns of left ventricular (LV) filling and emptying were studied in 17 patients with chronic anemia due to beta thalassemia and in 8 normal subjects. M-mode echocardio-grams were recorded in each patient and digitization and computer analysis of the tracings provided data relating to the systolic and diastolic performance of the LV. LV diameter was increased. The rate, pattern and time relationships of LV systolic emptying were normal or increased in patients with thalassemia especially in those with thalassemia major requiring a large number of blood transfusions. Peak LV filling rate and the time course of early diastolic ventricular filling were also normal or increased in most patients but an abnormality of diastole was present in 3; this may have been due to abnormal early diastolic relaxation or to right-sided overload altering the LV filling pattern.