The benefits of transfusion in AOP during BPD remain to be defined. Myocardial dysfunction has. been shown to be a sensitive and early indicator of the adverse effects of anemia. To determine the effects of AOP during BPD on myocardial as well as on the metabolic and erythropoietic functions, a study was planned to evaluate these parameters (mean±SEM) before (PR) and after (PO) a transfusion (20cc/kg of Packed RBC'S). Twelve anemic (Hb range: 71-88g/L) preterm infants (gest.age: 27.8±0.6 wks, birthweight: 1022±71.7g) were studied at a postnatal age of 6.6±0.5 wks with clinically stable BPD with O2 supplement (FiO2 30-35%). All measurements were done before and 48 hrs after the transfusion. Cardiac output(CO, L/kg/min), heart rate (HR,bpm) and myocardial function (mean velocity of circumferential fiber shortening, shortening fraction (SF%) and peak aortic velocity) were assessed by pulsed and continuous wave Doppler echocardiography. Resting O2 consumption (VO2, mL/kg/min), CO2 production (VCO2) and energy expenditure (REE, Kcal/kg/d) were obtained by indirect calorimetry. Hb-O2 affinity was assessed by determining P50 (mm Hg) by gas mixing tonometry. Erythropoietin (EPO)(mU/ml), 2,3DPG (μmol/g Hb) and lactate (mmol/L) were measured by RIA & enzymatically respectively. RESULTS: Table Lactate levels decreased from 1.6±0.2 to 1.0±0.1 (p<.01). This study showed that increased Hb level resulted in a suppression of EPO secretion (**p<.01). HR & CO decreased (*p<.05); there was a decrease in SF (p<.01) an indice of myocardial function. Weight gain / day× 7 days prior and after transfusion were similar (14.5±2 vs 15.3±1 g/kg/d). Metabolic demands as shown by VO2, VCO2 and REE were not affected. Transfusion of preterm infants with AOP and BPD decreases SF therefore diminishing the risk of high output cardiac failure. These findings could be of importance when establishing indications for transfusion for anemia of prematurity during BPD.