Objective To investigate MR imaging features of femoral marrow in treated ?-thalassemia major.Methods MR imaging of the proximal femoral marrow was performed in 35 cases of ?-thalassemia major and 45 age-and sex-matched normal children as control.Coronal images of femoral marrow with the techniques of spin echo and fast field echo(FFE)were obtained.On T_1-weighted imaging the red and yellow femoral marrow were judged and marrow distribution was classified into five groups.The hemosiderosis of marrow was judged on the basis of signal intensity of marrow on FFE imaging.The marrow distribution classification and the hemosiderosis on MR imaging were correlated with clinical features.Results On FFE,marrow hemosiderosis occurred in 15 patients with a marked hypo-intensity signal and was related to the age(P=0.032).On T_1-weighted imaging,the femoral marrow in 35 patients was classified as groupⅢand IV,while the marrow distribution was groupⅠorⅡin all normal children,there was statistically significant difference(P