Thalassaemia major determines an impaired effort tolerance because of a condition of severe anaemia, progressive left ventricular dysfunction, pulmonary circulation compromise. The aim of our study is to evaluate haemodynamic response to exercise in thalassaemic patients without clinical features of heart failure. We have selected 13 patients affected by thalassaemia major (Thal+; 10-18 years). Each patient was transfused when haemoglobin values were < 9-9.5 g/dl and was treated with desferrioxamine (40 mg/kg sc) when serum ferritin values were > 2,000 ng/ml. Thal+ patients were compared with normal subjects (Thal- 10-16 years). No patient assumed hypotensive therapy, no had familiar history of hypertension. Both groups have undergone an ergometric stress test at the cycloergometer, with increase of 25 W every 2 min, up to the reaching of the maximum age-related heart rate, or up to muscle exhaustion or unbearable dyspnea, followed by a 10 min recovery phase. The following parameters were taken in consideration: systolic (SBP) and diastolic (DBP) blood pressure, heart rate (HR), the product of the heart rate by the systolic blood pressure (DP), at rest, at the maximum common work (MCW), at maximum stress and in the recovery phases. At rest, only DP showed significant differences between the two groups: in Thal+ patients higher than in Thal- (p = 0.045). At the MCW, Thal+ patients had SBP (p = 0.019), DBP (p = 0.01), HR (p = 0.035) and DP (p = 0.003) higher than Thal- patients. At maximum stress only DBP showed significant differences in Thal+ patients (p = 0.019), although Thal+ patients achieved lower levels of workload (p = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)