Oral administration of beta-adrenergic receptor (?-AR) agonists to animals causes increased muscle and decreased fat mass in various combinations across species. Myostatin, a member of the transforming growth factor beta super family of growth factors, inhibits muscle growth. Researchers have created a mouse with the myostatin gene knocked out, which results in a double muscled phenotype with decreased fat mass and is an important model for both the agricultural and biomedical fields. Our objectives were to first determine if ractopamine, a ?-1 or clenbuterol, a ?-2 adrenergic receptor agonist would have similar, different, or any affects on the body composition of control mice. After discovering that clenbuterol had the same effect as ractopamine but at a lower dosage, the oral clenbuterol treatment was then tested on myostatin knockout mice. Our findings showed in both studies that fat pads were reduced, skeletal muscle mass did not change, and adipocyte apoptosis was increased when clenbuterol was administered.