Ethylene plays a key role in the rapid elongation of deepwater rice. We cloned cDNAs corresponding to at least three members of the 1-aminocyclopropane-1-carboxylate (ACC) synthase gene family of deepwater rice (Oryza sativa cv. Plai Ngam). Genomic DNA gel blot analysis confirmed the presence of a multigene family. Expression patterns were studied by Northern blot on poly(A + ) RNA prepared from plants exposed to abscisic acid, ACC, gibberellic acid (GA), indole-3-acetic acid, jasmonic acid, submergence and wounding. The mRNA levels were suppressed by ACC, GA, submergence and wounding, but remained relatively constant under all other conditions.