The effects of diethylstilbestrol (DES) and Synovex-S hormonal growth promotants on composition of body ash deposited by feedlot beef steers were studied in two slaughter-balance trials. Trial 1 consisted of three groups of eight Hereford steers averaging 225 kg initial body weight. One group was initially slaughtered (IS) at the beginning of the trial and two groups, control (C) and DES-treated (20 mg/steer daily in diet), were fed for 177 d and then slaughtered. Trial 2 consisted of 28 Hereford steers averaging 310 kg initial body weight. Four steers were IS and 24 steers were assigned to a factorial arrangement of treatments (- or + Synovex-S ear implant and - or + dietary kiln dust), fed for 126 d and slaughtered. Each Synovex-S ear implant contained 200 mg progesterone and 20 mg estradiol benzoate. Kiln dust (KD) was fed as a digestive tract buffer, and the +KD diets contained 1.23% Ca and .37% P compared with .45% Ca and .36% P in -KD diets on an as-fed basis. Mineral concentration in body tissue was greater for IS than for fed steers reflecting deposition of soft tissue, particularly fat, during the feeding period. Mineral concentration in body tissue was similar between C and hormonally-treated steers. Mineral composition of tissue ash in IS, C and hormonally-treated steers and composition of ash deposited during the feeding period for C and treated steers were similar. The results suggest that both DES and Synovex treatments of beef steers do not cause an increased propensity for skeletal growth but that ash deposition is of similar composition in C and treated steers.