The objective of the present research was to study the effect of planting dates on seed quality of three soybean cultivars representing different maturity groups. The experiments were grown under field conditions at Botucatu, State of São Paulo, Brazil (22o51?S latitude and 48o27?W.Gr. longitude), on a soil classified as ?Terra Roxa Estruturada? Soybean cultivars ?Paraná?, ?Santa Rosa? and ?UFV-1? were planted in intervals of 15 days on six planting dates, starting in October, and repeated for three years (1977/78, 1978/79 and 1979/80). The quality of harvested seeds was evaluated through germination and vigor (germination first-count and rapid aging methods) in laboratory, and the percentage of emergence of seedling in the field. Seed germination, vigor and field emergence increased from the first to the last planting date, with the best results being obtained in December plantings. These effects were particularly noticed for early maturing cultivar ?Paraná?, but were less defined for late maturing cultivar ?UFV-1?.