Beta-hydroxy-beta-methyl butyrate (HMB), a compound formed during catabolism of leucine, was fed to 256 crossbred steers as 0 or .03% of diet dry matter. Effects on performance, carcass characteristics, and tissue composition were measured. Groups of 32 steers per diet were slaughtered after 105, 119, 133, and 147 d on feed. The HMB was fed to each group only during the final 82 d they were fed. Averaged across slaughter date, animal performance was not altered by HMB; however, an interaction between HMB and time on feed was detected. Feeding HMB increased (P < .01) daily gain of steers slaughtered at 105 d but decreased (P < .01) daily gain of steers slaughtered at 147 d. Steers fed HMB had numerically higher marbling scores that resulted in a trend toward higher carcass quality grades. Steers receiving HMB tended to have less (P < .08) s.c. fat and fewer steers with yield grades of 4 or greater (1.6 vs 4.7%). Supplementation of HMB to feedlot steers tended to increase (P < .07) the ratio of intramuscular fat to subcutaneous fat. Steers fed HMB had higher (P < .001) blood plasma concentrations of HMB (3.06 vs 1.70 mg/L) and lower (P < .03) blood plasma concentrations of cholesterol (108.4 vs 118.7 mg/dL). Feeding HMB tended to increase (P < .10) lipid content of the longissimus muscles of those steers slaughtered at 105 d.