The fungus Cercospora kikuchii (Matsu. & Tomoyasu) Gardner, which causes the purple spot, is one of the most common soybean diseases in Brazil. However, studies conducted by the University of Illinois and Embrapa Soybean have shown that the fungus has no negative effect on seed quality. In a study by Henning et al. (1981), soybean seeds of the cultivars Paraná, Davis and Bossier, with 0,5, 10, 20 and 40% of purple spot did not differ with respect to vigor, germination and emergence in the field. In the same study, the transmission rate of this fungus in the seed-plant-seed system was considered irrelevant, since the highest rate of C. kikuchii infection observed in the harvested seed was 2.12%. For this reason, the purple spotted seed tolerance standard, previously required by law, was taken from the SAS (Seed Analysis Rules) by the SNPC/SARC/MAPA.