Waddington (1942) defined the term canalization as a measure of the ability of a genotype to produce the same phenotype regardless of variability of its environment. Molecular chaperons such as heat shock proteins (HSPs) are considered to be one of the molecular machineries of the canalization. Rutherford and Lindquist (1998) showed developmental abnormalities associated with deficits of Hsp90, and suggested the role of Hsp90 as an evolutionary capacitor. Hsp70, another Hsp gene, increases its expression under environmental stresses such as thermal and nutritional stresses, and may play an important role in developmental buffering as well as Hsp90. In this study, with Dsorophila melanogaster, we established deficiency line of Hsp70Ba using isogenic deficiency kit from DrosDel project, and examined the effect of the deficiency on fluctuating asymmetry (FA), an index of developmental instability, of bristle number and wing morphology under thermal and nutritional stresses. While FA for these traits was significantly larger in the deficiency heterozygote than in the wildtype, significant interaction was found between the deficiency and stresses, suggesting Hsp70Ba buffers developmental perturbations under specific environmental stresses.