The beta-adrenergic agonist, cimaterol, was fed to young growing pigs to determine whether the carcass compositional changes observed in finishing pigs fed a beta-adrenergic agonist would be manifest in young animals. Furthermore, because cimaterol increased the deposition of lean mass in finishing pigs, it could have a protein sparing effect in young pigs that are rapidly accreting muscle mass and have a high dietary protein requirement. Pigs were fed cimaterol (at 0, .25 and .50 mg X kg-1 diet) and either an adequate (18%) or restricted (14%) protein diet from about 10 to 60 kg body weight. Pigs that were fed the 14 compared with 18% protein diet grew slower and ate less but had the same gain-to-feed ratio. These pigs also had shorter carcasses, less lean muscle and more fat deposition (assessed by carcass measurements and carcass chemical composition) than pigs that received adequate protein. Plasma protein and albumin concentrations were greater and plasma cholesterol, triglyceride and fatty acid concentrations were lower in pigs fed high compared with low dietary protein. Dietary cimaterol had no effect on any of the growth or carcass variables or on adipose tissue metabolism. When fed the high protein diet, cimaterol-supplemented pigs had smaller livers and stomachs. Dietary cimaterol did not have any major detectable effects on these young pigs, nor was there any evidence for a protein sparing effect.