Two greenhouse and three field experiment were conducted to study the effects of elevated night temperatures on the yield and growth of a grain sorghum (Sorghum bicolor (L.) Moench) hybrid. The genotype used in these investigations was the 'RS 671' (Redlan x Tx 415), an open-pedigree temperate-adapted grain sorghum. The phenological growth phase during which temperature treatments were imposed was the panicle development (GS-2) period. Experiment I, II (greenhouse) and III (field) were designed to determine the response of grain sorghum to two elevated night temperatures and the growth stage during GS-2 period when the plant is most sensitive to elevated temperatures. Experiment IV and V (field) were conducted with the same objectives as those for Experiment I, II and III and also to determine the effects of artificial preconditioning on the plant's response to elevated night temperatures. Experiments I - Plants were exposed to 26.5 and 32 C night temperatures at 4-day durations commencing from florest differentiation through bloom. The two elevated night temperatures caused significant reduction in grain yield and yield components except seed size that was enhanced (12%) by the 32 C treatment. Approximately 19%, 21%, 24% and 20% reductions in panicle dry weight, grain yield per plant, number of seeds per panicle and grams of grain/GS-3 day/plant, respectively, were caused by the 32 C treatment. The 26,5 C treatment also caused reduction in these variables but to much lesser degrees. Numbers of days to (...).