This report describes how the degree of deacetylation and molecular weight of chitosan and the concentrations of sodium chloride and malic acid affect the formation of lyotropic chitosan liquid crystals. Chitosan samples of various degrees of deacetylation were prepared from P-chitin that was isolated from squid pens. They were degraded by ultrasonic irradiation to various molecular weights. The critical concentrations forming chitosan liquid crystals were determined with a polarized microscope. A chitosan sample with a degree of deacetylation of 67.2-83.6% formed cholesteric lyotropic liquid crystals when it was dissolved in 0.37-2.59M malic acid. The critical concentrations increased with increasing degrees of deacetylation of chitosan. They decreased with increasing molecular weights or increasing concentrations of sodium chloride and malic acid. (C) 2007 Wiley Periodicals, Inc.