Abstract 1. 1. To determine whether cyclic AMP mediates the effect of ACTH, bovine growth hormone and thyroid stimulating hormone (TSH) on protein synthesis in adipose tissue in a manner similar to its role in mediating the lipolytic effect of these hormones, glycerol release and amino acid incorporation into protein were determined in the presence of dibutyryl cyclic AMP and theophylline. 2. 2. ACTH, bovine growth hormone and TSH promoted [ 14C]histidine incorporation into protein of epididymal fat pads while they stimulated glycerol release therefrom. 3. 3. Dibutyryl cyclic AMP at 10 mM or at 1 mM plus added theophylline (2.5 mM) inhibited [ 14C]histidine uptake and incorporation into protein while enhancing glycerol release. 4. 4. The protein anabolic effects of ACTH, bovine growth hormone and TSH were abolished by theophylline. 5. 5. Low concentrations of dibutyryl cyclic AMP (0.1 mM) inhibited glycerol production in contrast to concentrations of 1 mM and above which had a stimulatory effect. Butyrate at 2 mM inhibited basal lipolysis.