Rice is extensively grown in irrigated cropping system, allowing production in the warmer, high radiation post-monsoon and summer months. Flowering (anthesis and fertilization) and to a lesser extent booting (microsporogenesis) are the most susceptible stages of development to temperature in rice which can induce floret sterility and limit grain yield. Hence this investigation was carried out in 98 heat tolerant genotypes of rice(Oryza sativa L.) to study the extent of variability, association, genetic diversity and effect of high temperature during anthesis. Seven genotypes (IR 86977 - 140 - 2, IR 86970 - 126 - 3, IR 86977 - 92 - 3, IR 86970 - 145 - 1, IR 86964 - 95 - 1, IR 86977 - 141 - 3 and IR 86977 - 104 - 1), which exhibited spikelet fertility of 15 - 40 % after exposure to high temperature stress(40 Degree Celsius), have been identified to be tolerant to heat or high temperature. All other genotypes were completely sterile. These genotypes offer scope for further utilization by hybridization or direct selection to develop high temperature stress tolerant rice to combat with the global climatic changes.