AbstractChitin membrane was prepared by casting aN,N‐dimethyl acetamide,N‐methyl 2‐pyrrolidone and lithium chloride (DMA‐NMP‐LiCl)solution of chitin and coagulating with several media. The effect of the coagulants on membrane formation was studied. 2‐Propanol was found to be more favourable than methanol, ethanol, acetone and mixtures of 2‐propanol and water. The membrane obtained in 2‐propanol was subjected to annealing. Annealing made the membrane dense and strong. The tensile strength of the membrane annealed at 145°C for 2hr was about twice that of an unannealed membrane. The solute permeability of the annealed membranes was lower than that of the original one. These phenomena could be clearly interpreted in terms