A novel polysaccharide-based polyelectrolyte complex was formed via ionic self-assembly (ISA) of a carboxylic derivative of starch, maleic starch half-ester acid (MSA), with chitosan (CS) and precipitated from aqueous solution. Both Fourier transform infrared (FTIR) spectroscopy and elementary analysis results showed that there was CS in the complex. Thermogravimetric analysis (TGA) showed that the thermal resistance of the complex was higher than that of two components and the corresponding blend. X-ray diffraction (XRD) analysis result revealed that the complex was amorphous, whereas its components were semi-crystalline. In addition, the drug release behavior of the complex that contains 5-fluorouracil behaved pH-responsive. All the experimental results verified the complex was composed of MSA and CS, and also indicated that the driving force for the self-assembly of the complex was predominantly the electrostatic interactions between two oppositely charged polyelectrolytes, cationic CS, and the anionic MSA. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 2255-2260, 2009