A limiting factor in wheat production in many countries is the occurrence of temperature stress at grain filling stage especially in West Asia and North Africa. In about 40% temperate environments constituting 36 million hectares, terminal heat stress is a major threat. Keeping in view this threat present investigations were made to explore sources of heat tolerance and its genetics.100 genotypes of wheat were screened in a plastic tunnel for heat tolerance by providing them heat stress at the time of anthesis. Selection of the genotypes was based on grain weight, number of grains per spike and grain yield per 25 spikes after computation of their relative ratios. The selected genotypes were also tested by measuring their electrolyte leakage to confirm the tolerance and susceptibility by calculating relative injuries. Seven genotypes including 3 heat tolerant, 1 moderately tolerant and 3 susceptible were crossed in a 7 × 7 diallel fashion.The information obtained from these results during the current studies may be used to evolve high yielding varieties which can produce higher yield and help maintain yield sustainability in those areas where terminal heat stress is a major threat.