Abstract: The polyamines of pilose antler (PASPA) consist of putrescine (PU, 70.9%), spermidine (SPD, 26.3%) and spermine (SP, 2.8%). The incorporations of ³H leucine into protein and ³H uridine into RNA in mouse liver tissue were increased when PASPA was given orally to mice at the dose of 30 mg/kg for 4 successive days. The incorporations of ³H leucine into liver protein and ³H uridine into the cytosolic and nuclear RNA were also increased by treatment with PU (21 mg/kg). In addition, the RNA polymerase activity in the solubilized liver nuclear fraction of PU (21 mg/kg)-treated mice was increased. SPD only promoted the synthesis of protein in mouse liver tissue at the dose of 8 mg/kg. However, SP showed no effect on the synthesis of protein and RNA polymerase activity under the used dose (1 mg/kg). The results suggest that PASPA is the main active substance responsible for the promotion of the synthesis of protein and RNA in mouse liver.