We evaluated 27 patients (pts.) with thalassemia major (TM) aged 18 to 38 years (mean 28 ±5.9) who received deferroxamine (DFO) chelation for 13-24 years (mean 17.5±2.03) by ECG, continuous Holter monitoring (HM), echo-cardiograms (echo) and signal averaged ECG's (SAECG). Mean pre-transfusion hemoglobin over a one year period ranged from 8.4 to 10.8gm/dl, serum ferritins ranged from108 to 7584 ng/ml (mean 1424.7, median 889) and the ratio of the total transfused iron (Fe) to cumulative DFO use ranged from 9.37 to 22.91 mg.Fe/gm.DFO (mean 13.4±3.42). Systolic function as measured by shortening fraction (SF) was abnormal in only 1pt., but the ratio of mean velocity of circumferential fiber shortening to end systolic wall stress was abnormal in 3, including the patient with the low SF. The early and late atrial filling velocities were increased but their ratio, isovolumic relaxation time and the deceleration time were normal in all indicating the absence of restrictive diastolic abnormalities.The left ventricular mass as calculated by the echo was normal in all.By HM, supraventricular premature beats(PB) and ventricular PB's were noted in 9, but the latter were Grade 2 or less of Lown's classification in all but 1 pt.The mean QRS duration(QRSD) and the duration of the low amplitude signal below 40μV(LPD40) were significantly different between the pts. and the control{98.9±14.3 vs 89.7±5.5mSec for QRSD(p<0.04);31.6±13.0 vs 23.0±7.5 mSec for the LPD40(p<0.04)}.Six pts. had late potentials in their SAECG's. None of these 6 pts. had any evidence of systolic or restrictive diastolic dysfunction as observed by echo; however 5 of these were over the age of 24 years. In only 3 of these 6 pts.was ventricular arrythmia detected by HM.Conclusions: Thus, in well chelated pts. with TM there appears to be a remarkably good preservation of systolic and diastolic function with freedom from serious arrythmia well into the third decade. The 6 pts. with the late potentials bear close monitoring.