Chitosan, a cationic polysaccharide, was heterogeneously deacetylated with a 47% sodium hydroxide solution and followed by a homogeneous reacetylation with acetic anhydrides to control the N-acetyl content of the chitosan having a similar molecular weight. The chitosans having different degrees of N-acetylation were complexed with sodium alginate, an anionic polysaccharide, and the formation behavior of polyelectrolyte complexes (PECs) was examined by the viscometry in various pH ranges. The maximum mixing ratio (Rmax) increased with a decrease in the degree of N-acetylation of the chitosan at the same pH, and with a decrease in pH at the same degree of N-acetylation. Similarly, N-acylated chitosans were also prepared. The N-acyl chitosans scarcely affected the formation behavior of PECs with sodium alginates. For the application of the PECs produced, the microencapsulation of a drug was performed and the release property of drug was tested. The microcapsules were prepared in one step by the extrusion of a solution of guaifenesin and sodium alginate into a solution containing calcium chloride and chitosan through interpolymeric ionic interactions. The drug release during the drug-loaded microcapsules storage in saline was found to depend on the pH where the microcapsules were formed and the kind of N-acyl groups introduced to the chitosan. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 425–432, 1997