Date of planting and plant density are two cultural practices influencing grain yield of maize (Zea mays L.) . Our study was designed to evaluate the usefulness of a mass selection scheme to improve cold and density tolerance of the BS2 and BS3 maize populations . Populations were planted at an early planting date and a high plant density, and three cycles of mass selection for well-filled ears on erect plants were conducted at each of three Corn Belt locations (i .e ., Waseca, MN ; Ames, IA ; Portageville, MO).Results showed that selection improved cold tolerance traits of BS3, but not of BS2 . Mass selection did not increase density tolerance of either population at any location . Selection did not improve response to planting dates, although the early planting date did improve agronomic performance and grain yield of all entries . We concluded that mass selection at high plant densities and early planting dates at diverse geographical locations did not produce cycles adapted to specific environmental conditions .