Taxol, the extract from the Taxus brevifolia which is a Pacific yew tree has aroused the interest of the tumor investigators since the 1960s. As well, it is shown to have broad antitumor activity in preclinical experimental models. Its action mechanism is an anti-microtubule effect by duplication of tubulin. The most impressive antitumor activity of taxol has been observed in advanced ovarian cancer and metastatic breast cancer. The purpose of this study was to determine how taxol acts on malignant bone tumor cell lines, to compare its cytotoxic effect with those of other chemotherapeutic agents, and to ascertain the its combination effect with adriamycin. Cell lines used in this study were G-292(osteosarcoma, human), SaOS-2(osteosarcoma, primary, human), and HT-1080(fibrosarcoma, human). Methotrexate, adriamycin, cisplatinum, ifosfamide and taxol were used as testing chemotherapeutic agents and their maximum test concentration were $500{\mu}g/ml$, $200{\mu}g/ml$, $500{\mu}g/ml$, $1000{\mu}g/ml$, and $600{\mu}g/ml$, respectively. The media for cell culture was RPMI-1640 with 10% fetal bovine serum and gentamycin. The results were as follows. The $IC_{50}$ of methotrexate, ifosfamide, cisplatinum, adriamycin and Taxol in G-292 were $2.3{\times}10^{-1}{\mu}g/ml$, $8.0{\times}10^0{\mu}g/ml$, $3.5{\times}10^0{\mu}g/ml$, $9.8{\times}10^{-1}{\mu}g/ml$, $2.7{\times}10^{-2}{\mu}g/ml$ respectively, in SaOS-2 $3.5{\times}10^{-1}{\mu}g/ml$, $1.5{\times}10^1{\mu}g/ml$, $2.8{\times}10^0{\mu}g/ml$, $9.9{\times}10^{-2}{\mu}g/ml$, $1.0{\times}10^{-2}{\mu}g/ml$, respectively, in HT-1080 $4.2{\times}10^{-2}{\mu}g/ml$, $5.4{\times}10^1{\mu}g/ml$, $3.8{\times}10^0{\mu}g/ml$, $5.5{\times}10^{-3}{\mu}g/ml$, $1.1{\times}10^{-3}{\mu}g/ml$, respectively. In conclusion, taxol had very potent cytotoxic effect on the malignant bone tumor cell lines with adriamycin, and was more potent than methotrexate, cisplatinum and ifosfamide. There were synergistic antitumor effects on G-292 and SaOS-2 cell lines in combination test of taxol and adriamycin. From the above results, it would be estimated that taxol could be a new antitumor drug for the malignant bone tumors, providing measures against the side effects and followed by the clinical tests.