A field experiment was carried out during kharif seasons of 2005 and 2006 to study the effect of heat and thermal unit use of maize cultivars in red sandy loam soil at Zonal Agricultural Research Station, Shimoga (Karnataka, India). The experiment consisted of three dates of sowing viz., first fortnight of June, second fortnight of June and first fortnight of July with six cultivars viz., two double cross hybrids (All-rounder and 30 R-77), two single cross hybrids (NAH-2049 and 30 V-92) and two composites (NAC-6004 and NAC-6002) was laid out in split-plot design replicated thrice. Higher heat use efficiency was recorded with the crop sown in first fortnight of June and decreased with each delay in sowing. Grain yield of maize was found inversely related to the helio-thermal units. Thus, early sowings escape adverse situation during its life cycle in maize.