In addition to spherulites, two novel crystalline morphologies, i.e. need-like crystal and sheet-like crystals were found in formic acid solution cast films of N-methyl chitosan and N-ethyl chitosan during casting at 25degreesC and relative humidity 65%. Their size was larger in 1-2 order of magnitude than chitin needle-like single crystals and chitosan lamellar single crystals reported previously due to the high molecular weight. The formation mechanism of these crystalline morphologies was discussed.