In the growing season of 1990/91 an experiment was conducted in the Federal University of Viçosa to evaluate the physiological and sanitary quality of seeds of soybean genotypes with different degrees of seed coat impermeability. The varieties Doko, Savana, UFV-1 and UFV-10 with permeable seed coat, and IAC-14 and the breeding lines IAC 80-3110, TG x 849-9D and TG x 849-41D with impermeable seed coats were submited to four harvesting times: at the R8 stage and 15, 30 and 45 days after that stage. The physiological and sanitary quality of seeds were evaluated in laboratory by the standard germination test (paper towel), accelerated aging test and seed health test (blotter test). Seedling emergence in sand and the speed of germination index were evaluated in greenhouse. The breeding lines TG x 849-9D and TG x 849-41 D, slightly superior to the variety Doko, were the most promising in the maintenance of the seed viability and vigor with the delayed harvest. On the other hand, the variety Savana and une IAC 80-3110 showed lower tolerance to deterioration in the field. Seed coat impermeability was not the only factor responsible for physiological seed quality. The 45-days period of delayed harvest after R8 stage was the most appropriated to differentiate the genotypes with better seed quality.