Postnatal muscle hypertrophy of beef cattle is the result of enhanced myofibrillar protein synthesis and reduced protein turnover. Skeletal muscle hypertrophy has been studied in cattle fed ${eta}$-adrenergic agonists (${eta}$-AA), which are receptor-mediated enhancers of protein synthesis and inhibitors of protein degradation. Feeding ${eta}$-AA to beef cattle increases longissimus muscle cross-sectional area 6% to 40% compared to non-treated cattle. The ${eta}$-AA have been reported to improve live animal performance, including average daily gain, feed efficiency, hot carcass weight, and dressing percentage. Treatment with ${eta}$-AA increased mRNA concentration of the ${eta}_2$ or ${eta}_1$-adrenergic receptor and myosin heavy chain IIX in bovine skeletal muscle tissue. This review will examine the effects of skeletal muscle and adipose development with ${eta}$-AA, and will interpret how the use of ${eta}$-AA affects performance, body composition, and growth in beef cattle.