Soybean mutants with high seed germination and vigor Chiang Mai 60 is a high yielding soybean variety in Thailand. However, it has a poor character of seed germination and vigor. Then induced mutation was used to improve seed quality of the variety, seed of Chiang Mai 60 was irradiated with 100 gray. Pedigree method of selection was used in late generations of M4-M6 at Chiang Mai FCRC. Accelerated Aging Test was also used to test the seed vigor of the mutant lines. A total number of 23 mutant lines were finally selected. In preliminary trials conducted in dry season 2006, eight mutant lines had seed germination of 65-80% compared with the original parent of 30%, whereas in rainy season 2006, 12 mutant lines had seed germination of 75-89%, and the parent gave only 41% [8]. The selected mutant lines are being tested for their yield in standard trials.