Endocrine function was evaluated in 20 prepubertal patients with homozygous beta-thalassemia treated with frequent transfusions and long term iron chelation therapy. FSH, LH, PRL, and TSH secretion were evaluated by LRH and TRH testing and L-dopa and ACTH were used to assess GH and adrenocortical reserve. No statistically significant differences were found between FSH, LH, PRL, GH, and cortisol secretion in the patients and in normal subjects. There was a relatively high incidence (35%) of primary thyroid impairment since 1 patient had primary hypothyroidism and 6 others had evidence of subclinical hypothyroidism as manifested by increased TSH responses to TRH. However, no statistically significant correlations were found between either serum ferritin levels, total blood transfusions received, and thyroid function.