Leaf rust, caused by Puccinia triticina E., is an important disease of wheat in Japan. Thirty Japanese wheat (Triticum aesticum L.) cultivars, 7 Japanese supplementary differentials and a set of near-isogenic lines carrying named Lr-genes, were evaluated for resistance at the seedling growth stage with an array of Mexican Puccinia triticina races. The variation in seedling infection type of the cultivars was compared with that of the differentials, and genes conferring a low infection type were postulated. In total, nine named genes, viz. Lr1 (2 cultivars), Lr3 (3), Lr9 (4), LrlO (5), Lr17 (1), Lr19 (1) Lr23 (8), Lr27 + 31 (3) could be identified/postulated in Japanese cultivars and supplementary differentials.