Degenerate primers were used to amplify by the polymerase chain reaction (PCR) DNA fragments from the chitinase genes of five insect species: Aedes aegypti, Anopheles freeborni, Anopheles gambiae, Anopheles stephensi and Drosophila melanogaster. As many as four different products were found for each species; each deduced protein sequence having greatest homology to chitinase sequences from other species of insects and the crustacean, Penaeus japonicus. The four PCR products of A. aegypti hybridize to two loci, with three of the products derived from either three tightly linked genes or a single gene with three catalytic domains. Southern blot hybridizations of the PCR products from the species of Anopheles suggest a similar arrangement.