Heat shock protein 70 (hsp 70), is the major protein expressed when cells are heat-shocked. We tried to isolate hsp 70 cDNA from mouse fibroblast ID13. ID13 cDNA library was screened with human hsp70 gene as a probe, and a positive clone was obtained. The positive clone was subcloned into pUC19 and the precise restriction map was obtained. The cDNA gene was sequenced by Sanger dideoxy termination method. A single long open reading frame that could code for a protein of 643 amino acids was found. The sequence of cloned mouse hsp70 shows great homology (60-97\%) with other mouse hsp 70 genes and somewhat less homology (50\%) with E. coli hsp 70 gene (dnaK). The great homology (97\%) with already cloned mouse heat shock cognate 70 kDa protein (hsc 70) make us to think that the cloned gene is constitutively expressed at normal temperature.