Objective To observe the in vitro growth inhibitory and apoptois-inducing effcts of paclitaxel on the human osteosarcoma cell line U-2 OS Methods U-2 US cells were treated with vadous concentrations of paclitaxel Proliferatien was determined by cell count in a neubauer eytometer chamber Viability was assessed by trypan blue dye exclusion Paclitaxel-induced morphotogic alterations were visualized using light and transmission electron microsopy. The extent of paclitaxel-induced apoptosis was determined by flow cytometry and immunohistochemical duration (Td T-mediated dUTP nick end labeling technique, TUNEL) Results The cells treated with pacifies[ initially showed G2/M arrest, which was followed by apoptosis. The characteristic apoptotic changes, including nuclear disintegration and chromatin agglomeration, were displayed. Large amounts of micronuclei cells appeared, something not observed in those cells treated with eispiatin and adriamycin for contrast. Also, extensive DNA-cleavage was detected using TUNEL. Conclusion This study demonstrates that pacliaxel has an apoptotic-inducing effect on osteosarcoma cells through the initiation of G2/M arrest and inhibiting mitosis in both a time-depsndent and dose-deoendent manner.