In this article, syntheses of chitin acetate/butyrate copolymers with different contents of acetyl residue in polymer chain have been described. Chitin copolymers as well as pure diacetylchitin (DAC) and dibutyrylchitin (DBC) have been obtained in the reaction of shrimp chitin with mixture of acetic and butyric anhydrides used in different proportion. Reactions have been carried out under heterogeneous condition with perchloric acid (PA) used as a catalyst of reaction. Chemical structure of DAC, DBC, and co-(acetate/butyrates) was confirmed in H-1-NMR as well as in Fourier transform infrared (FTIR) investigations. Results of H-1-NMR investigation showed that in all cases of chitin esterification carried out at applied conditions, final products with summary degree of substitution (DP) closed to 2 have been obtained. Prepared chitin acetate/butyrate copolymers with high degree of polymerization (DP) (based on value of intrinsic viscosity) with varying amount of acetyl groups from 0.24 to 1.29 have been formed depending on the mixture composition of acetic and butyric acid anhydrides. All obtained co-(acetate/butyrates) are soluble in organic solvents such as dimethylformamide (DMF), dimethylsulfoxide (DMSO), dimethylacetamide (DMAc) as well as ethanol and form strong transparent films. It was stated that solubility of obtained chitin copolyesters slightly decreases with increase of the acetyl groups content in polymer chain, but it is still high enough to be taken into consideration for eventual production of fibers or scaffolds. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 175-182, 2011