Chitosan microspheres (CM) and reacetylated chitosan microspheres (ACM) were successfully made by the methods of oil/water emulsification and acetic anhydride. The characteristics of the microspheres as a drug carrier system were investigated. Two microsphere samples had spherical shape with the mean diameter of 80.79 mu m for CM and 81.25 mu m for ACM. The in vitro degradation (pH 7.4) in the presence of lysozyme showed a slow mass loss and ACM was higher degradation compared to CM. The microspheres, especially ACM, had a high drug loading capacity of Adriamycin hydrochloride (ADM) (12.4%) and had sustained release. The cytotoxicity was evaluated in vitro via MTT assay, ACM with steadily continual adhesion to cells had no fibroblast cytotoxicity. The inhibitory rates of ADM-loading CM, ACM suspension to Tca 8113 cells were significantly outperformed that of ADM solution.