Genetic variation in total mRNA level of the six hsp genes (hsp22, hsp23, hsp26, hsp27, hsp70 and hsp82) in the presence of heat shock was investigated by using seventy-four second- and seventy third-chromosome lines of Drosophila melanogaster which have the same genetic background derived from a highly inbred stock. There was significant variation in all the six hsp genes for both the second- and third-chromosome lines except for the hsp22 gene of the third-chromosome lines. Although all the structural genes of the heat shock proteins are localized on the third chromosome, the estimates of genetic variance for the second-chromosome lines were larger than those for the third-chromosome lines. Highly significant correlations between total mRNA level of the different hsp genes in all the combinations of the six hsp genes using the second-chromosome lines were found, but some of correlations for the third-chromosome lines were not significant. These results suggest that some second chromosome variants have similar effects on the expression of the different genes.