Chitosan (CS) colloidal carriers, which consist of an oily core and a CS coating, were developed to facilitate a controlled intracellular delivery of docetaxel. The systems presented a particle size of <200 nm and a positive surface charge. As shown by the flow cytometry analysis, fluorescent CS carriers were rapidly internalized by human tumor cells. Fluorescence was observed in more than 80% of MCF7 (human breast adenocarcinoma) and almost 100% of A549 (human lung carcinoma) cells when a 2 h treatment with fluorescent CS carriers was given. A total of 24 h after treatment, docetaxel-loaded CS carriers had an effect on cell proliferation that was significantly greater than that of free docetaxel. These results indicate that docetaxel remains fully active upon its encapsulation into the colloidal carriers and that these systems actively transport docetaxel into cancer cells and, thus, result in a significant increase in its antiproliferative effect.