Ideal corn (Zea mays L.) planting dates vary by region and frequently require updating. Two non-GMO corn hybrids and two Bt [Bacillus thuringiensis (Berliner)] hybrids of three maturity ranges, short-season (1180-1270 GDU 10's), mid-season (1455-1470 GDU 10's), and full-season (1540-1625 GDU 10's) were evaluated for yield, yield components, and mycotoxins in 2002, 2003, and 2004 at Stoneville, MS. Plots were planted in a furrow irrigated split-plot of a randomized complete block design replicated 4 times. Whole plots were plantings in early April, mid-April, or May, while sub-plots were hybrids randomly assigned. Experimental units were four 102 cm rows, 9.1 m long. Growing degree units of a 10 C base (GDU 10) at silking and physiological maturity were calculated. Lodging and dropped ears were inconsequential. Yields were greater for mid-April plantings (8.9, 9.1, and 9.2 Mg ha^-1) than May plantings (7.9, 8.1, and 7.4 Mg ha^-1) in 2002, 2003, and 2004 respectively but not early April plantings in 2002 and 2004 (8.7 and 9.5 Mg ha^-1 respectively). Short season hybrids generally yielded less than mid-season or full season hybrids. The Bt hybrids yielded more than non-GMO hybrids (9.4, 9.0, and 9.0 Mg ha^-1 vs. 7.7, 7.6, and 8.5 Mg ha^-1 in 2002, 2003, and 2004 respectively). Yields correlated with GDU 10's at silking [yield=0.037x-20.416 (r=0.77)] but not physiological maturity. Aflatoxin was high in 2002 (224.0 mg Mg^-1), and much less (28.8 and 7.4 mg Mg^-1) in 2003 and 2004 respectively. The Bt hybrids had less fumonisin contamination than non-GMO hybrids (5.2 vs. 8.5 mg kg^-1) but had less aflatoxin only in 2003 (12.4 vs. 45.3 mg Mg^-1).