Response of rice varieties Tongil, Jinheung and IR 24 to four preemergence herbicides was determined. Saturn-s [s-(4-chlorobenzyl)-N, N-diethylthiol carbamate plus 2-methylthiol-4, 6-bisethylamino-2-triazine] caused severe injury to Tongil at the high temperature and less at the higher water level, but slight injury to Jinheung and IR 24. The difference may be explained by the shallower root system of Tongil, allowing more contact with the herbicide, or different varietal metabolic rates.