Two experiments were conducted to assess the genetics of heat stress survival time (HSST) and its relationship to body weight (BW) in Japanese quail. In Experiment 1, Japanese quail from the Athens Randombred population were used and estimations of heritability (h2) and genotypic correlation (rg) were based on half-sib relationships. Three lines of Japanese quail selected under different environments and the Athens Randombred line were studied in Experiment 2. Estimations of h2 and rg were based on full-sib relationships. Heritability for HSST was moderate (.28 to .53) in Experiment 1 and low in Experiment 2 (.13 to .24). Phenotypic correlations between HSST and BW ranged from -.33 to -.05, and a negative genotypic correlations between HSST and BW suggested that selection for longer HSST would result in reduced BW.