A complementary DNA encoding an ethylene-inducible acidic chitinase of azuki bean (Vigna angularis) was isolated, and its complete nucleotide sequence was determined. The nucleotide and deduced amino-acid sequence were very similar to those of an acidic chitinase from cucumber leaves that had been infected with tobacco necrosis virus. The mRNA for the acidic chitinase was not detected in leaves of azuki bean that had not been treated with ethylene, but it appeared 3 h after initiation of treatment with ethylene and its level gradually increased over a period of 19 h. The mRNA also accumulated in response to salicylate or wounding. The expression of the gene in response to wounding was suppressed by 2,5-norbornadiene, but that in response to salicylate was not affected by this inhibitor.