Growth and sexual development were evaluated in 250 adolescents with beta-thalassemia major. Before transfusion hemoglobin concentration had not been less than 9.5 gm/dl in the last 5 years; desferrioxamine had been administered for 7 to 10 years, including by the subcutaneous route for 3 years. Thirty-seven percent of patients were found to be 2 SD below the mean for normal height; after age 14 years the percentage was 62% for males and 35% for females. Eighty-three percent of males and 75% of females had delayed skeletal maturation. Complete lack of pubescent changes was present in 38% of females and 67% of males aged 12 to 18 years. Only 19% of females had experienced menarche; secondary amenorrhea intervened in a third of them. A multiple regression analysis of indicators of pubertal development with age, age at first transfusion, age at splenectomy, number of transfusions, serum transaminase and ferritin, and duration and intensity of chelation therapy failed to identify the factors responsible for the variation observed in sexual maturation among patients with thalassemia.