Insulin and adenosine are both antilipolytic when studied in the epinephrine-stimulated perifused isolated fat cell. Sub-maximal combinations of insulin plus adenosine are additive but not synergistic. The polypeptide hormone insulin produces an antilipolytic effect which manifests itself as a “lag” in restoration of epinephrine-stimulated lipolysis after removal of the insulin. No such lag is observed with the non-peptide, small molecular weight adenosine. Herein, we demonstrate the antilipolytic effect of two distinct, physiologically important agents in the perifused isolated fat cell.