This study was carried out to evaluate cytotoxic effects of Poncirus trifoliata Raf. extract on lymphocytic leukemia tumor (L1210) cell lines. Disruptions in cell organelles were determined by 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl-2H-tetrazoliumbromide (MTT) assay The comparison of Ic50 Values of Poncirus trifoliata Raf. extract in L1210 cell lines showed that their susceptibility to these fractons decreased in the following order: adriamycin > Fr.4> Fr. 6> Fr. 5> Fr. 3> Fr. 1> Fr. 2 by the MTT assay. In order to develop an antumicrobial agent, Poncirus trifoliata Raf. was extracted wit ethanol, and then it was fractionated with several mobile phase. The antitumor activities of fractions of the ethanol soluble extract was investigated. The minimal inhibitory concentrations (MIC) of fractions of the ethanol soluble extract of Poncirus trifoliata Raf. against microorganisms were also examined. Antimicrobial activities of ampicillin and ketoconazole as references were compared to those of fractions of the ethanol soluble extract of Poncirus trifoliata Raf. The antimicrobial activities of all fractions from the extract had growth inhibition activities against gram-positive bacteria, gram-negative bacteria and fungi $(MIC;>;200{mu}g/ml)$. These results suggest that fraction 4 of the ethanol soluble extract of Poncirus trifoliata Raf. possessed the most antitumorous agent.