Genetics of submergence tolerance in rice was studied by analysing the segregation pattern of F 2 and backcross populations of three crosses involving tolerant cultivars BKNFR76106-16-0-1-0, FR13A and Kurkaruppan, and susceptible cultivars IR42 and Nona Bokra. Mortality of plants under completely submerged conditions was used to characterize tolerance of 15- and 50-day-old plants. Submergence tolerance was found to be governed by a single dominant gene.