In homozygous beta thalassemic patients we examined the role played by the interaction of ER gene polymorphisms with adverse environmental factors. A total of 108 homozygous beta thalassemic patients, 60 prepubertal mean age 9,5 +/- 3,7 years (27 M, 33 F) and 48 pubertal mean age 22,2 +/- 5,4 years (21 M, 27 F), regularly treated with red cell transfusion and iron chelation therapy were segregated on the basis of their XbaI and PvuII ER gene polymorphisms. Body mass index (BMI), lipidic pattern and blood pressure values were evaluated in each group. No significant differences were observed between patients segregated by their PvuII ER genotypes. Prepubertal and pubertal patients of both sexes lacking XbaI site showed BMI, HDL, LDL cholesterol significantly different than the other patients. In addition, triglyceride levels and blood pressure values were significantly higher in pubertal patients of both sexes lacking XbaI site than in other patients. ER XbaI polymorphism appear to influence nutritional factors, metabolic status and blood pressure and could be considered additional risk factors for later cardiac involvement in beta thalassemic patients.