Soybean (Glycine max L. Merril) cultivars IAC-8, UFV-1 and DOKO were planted in October 10th, October 30th, November 20th, December 12th and December 30th, in 1980/81 and 1981/82 at the EPAMIG Experimental Station, in Uberaba-MG, with the objective of determining the influence of planting date on the quality of the seed produced. The evaluations comprised germination and seed vigor tests. The Blotter test was utilized for the sanitary evaluation. There was a significant ?cultivar x planting date? effect indicating that cultivars behaved distinctly as far as seed quality was concerned, when planted in different dates. Neverthless, seed of all cultivars studied, when planted at October 10th, presented a decrease in seed quality as compared to the ones sown after November 20th. Seed of good quality was produced on November and December planting dates, since harvest season ranged from April 15th through May. At this time, the crop escaped from heavy rains and consequently from incidence of microorganisms (specially Phomopsis sp). The results of this study also indicated that seed germination and vigor were inversely proportional to the occurrence of that pathogen.