Serum samples were obtained from 30 burned men at different times up to the fourth month after injury. Mean concentrations of estradiol (E2) were elevated above those for healthy control subjects. Mean serum total testosterone (T), sex hormone-binding globulin (SHBG), bioassayable luteinizing hormone (LH), thyroxine (T4), triiodothyronine (T3) and their free indices (FT4I and FT3I) were depressed below those of controls during the first postburn week. Mean values for T and LH were progressively higher in samples taken from later time periods but remained depressed. Mean SHBG and thyroid hormones rose and were not significantly different from control values during later periods of the study. Calculated non-SHBG-bound T (NSBT) was below normal in each time period. The close correlation of SHBG values with those of T3 and FT3I in the patients suggests that SHBG responds to the altered thyroid hormone milieu of burn injury. It is postulated that elevated serum E2 perhaps from adrenal precursors promotes an alteration of hypothalamic function resulting in a markedly reduced secretion of bioactive LH and diminished Leydig cell function.