Considering the difficulties in the production of high quality soybean seeds, in the period of traditional cultivation in some areas of Paraná State, a work was accomplished with the objective of evaluating the influence of sowing dates in the physiological quality of the seeds of five soybean cultivars, and also establish the better sowing period to produce seeds with higher quality in Maringá-PR region. For that, were conducted five cultivars assay in the agricultural year of 1998/99, in randomized blocks design. Each assay was sowed in different dates (15/10, 30/10, 15/11, 30/11 and 15/12). The evaluated cultivars were: BRS-132 (precocious), BRS-133 (semi-precocious), BR-16 (semi-precocious), BRS-134 (medium) and FT-Estrela (late). The seeds obtained in the different sowing dates were evaluated, in laboratory, by means of germination test, first germination count, classification of seedling vigor, accelerated aging, seedling length and dry mass and visual quality of the seeds. The conclusion is that the sowing accomplished in the period between November nine and 27, depending on the cultivar, went more favorable to obtaining
seeds with superior physiological quality in the area of Maringá - PR. Cultivar BRS-133 presented the greatest stability in the seeds production with better quality in the different evaluated sowing dates. Cultivars BRS-134 and BRS-133, in the period of 15/10 to 30/11, presented higher percentage of normal seedling in the germination, classification of seedling vigor and accelerated aging tests.