The effect of L-arginine on the arginase activity and polyamine levels was studied in the pancreas of normal and diabetic rats (120 mg/kg alloxan, i.v.). Four groups were formed (10 male adults per group). I-Control-0.154 M NaCl. II-Diabetic-0.154 M NaCl (96 h after alloxan). III-Control plus 10 mM L-arginine IV-Diabetics plus 10 mM L-arginine. Rats were sacrificed 20 min after L-arginine injection. Glucose in serum and dry weight, proteins, arginase activity and polyamines (HPLC) in pancreas were measured. Higher ratio mg protein/mg dry weight and arginase induction was observed for groups III and IV. Putrescine was low as a consequence of diabetes but restored with L-arginine. The concentrations of spermidine and spermine were lower. These results may suggest that arginine is metabolized to putrescine in the pancreas and that polyamines may be utilized in regenerating processes or for recovering the endocrine pancreatic function.