We have established the quantitative method for assay antimutagenic activity from natural products using SOS chromotest technique. Establishment of the method in this study makes it possible to numerize antimutagenic activities from samples in term of the sample amount required for 50% inhibition to mutagenic activity induced by the chemical mutagen under the standard assay condition. Antimutagenic activities of rices from different cultivars as well as other cereals were assayed through this method. The results revealed that antimutagenic activities of mutant cultivar, Suwon 393(Hyangdo) and Sanghaehyanghyulla(Jado). were higher than Chuchung which mainly consumed for steamed rice, and also indicated that antimutagenic activities of cereals, such as job tear, buckwheat, small red bean, black bean were generally higher than that of brown rice.