In this study, chitosan microspheres were prepared by a suspension crosslinking technique. A petroleum ether/mineral oil mixture was used as the suspension medium which includes an emulsifier, e.g. Tween-80. Glutaraldehyde was used as the cross-linker. 5-Fluorouracil was incorporated in the matrix for the possible use of the microspheres in chemoembolization. The size and size distribution of the chitosan microspheres varied in the size range of 100-200 mu m, by changing the emulsifier concentration, stirring rate, chitosan/ solvent ratio and drug/chitosan solution ratio. In summary, the size and size distribution of the microspheres decreased when the emulsifier concentration and stirring rate were increased. Smaller microspheres with narrower size distributions were obtained when the chitosan/solvent ratio and drug/chitosan ratio were lower. It was possible to load the chitosan microspheres with 5-FU to a concentration of 10.4 mg 5-FU/g chitosan. Around 60% of the loaded drug was released within the first 24 h, then the release rate became much slower.