A rice mutant lacking alcohol dehydrogenase (ADH) was isolated by screening the M2 Iines of the rice cultivar Kinmaze that had been treated with N-methyl-N-nitrosourea. The mutant seedling lacked all of three isozymes of ADH, and was estimated to carry a single recessive mutation. Germination of mutant seeds was severely suppressed when seeds were submerged. However, mutant seedling survived under submergence for seven days and grew normally when transferred to aerobic conditions. These results indicate that ADH is essential for germination under anaerobic conditions but is not a prerequisite for growth under aerobic conditions.