Abstract: OBJECTIVE To investigate into the in vivo and in vitro anti-tumor effect of pine bark procyanidins.METHOD MTT chromatometry was adopted to observe the inhibiting effect of pine bark procyanidins on multiple human tumor cell strains and mice tumor models were used to study the inhibiting effect on mice S180 sarcoma and EAC ascites carcinoma.RESULT Pine bark procyanidins had inhibiting effect on a number of human tumor cells,with the maximum inhibiting rate of 60%. At the dosage of 200 mg/kg,it could markedly inhibit the growth of mice S180 sarcoma,with an inhibiting rate of 42.3%.However,had no marked effect on the survival time of mice with EAC ascites carcinoma.CONCLUSION Pine bark procyanidins has certain in vivo and in vitro anti-tumor effect.