Full-length cDNA for a 70.6 kDa heat-inducible heat shock protein (HSP70), a member of the HSP70 family, was isolated from a cDNA library of cultured cells in early passage originated in Japanese flounder embryos (JFE cells). It has a single ORF of 1920 bp that encodes a protein of 70.6 kDa. Japanese flounder HSP70 contains an EEVD peptide motif at C-terminal end which is a common feature of the cytosolic HSP70 family. Japanese flounder HSP70 is 86.0%, 83.8%, and 83.6% identical in primary structure to chinook salmon HSP70, bovine HSP70, and human HSP70, respectively. Japanese flounder HSP70 is also 83.6% identical to Japanese flounder HSC71. These results suggest that the amino acid sequence of the cytosolic HSP70 family, HSP70 and HSC71, has been highly conserved among vertebrates. Northern blot analysis showed that HSP70 mRNA was induced with heat shock treatment in the JFE cells in early passage.