The amino acid sequences of peptides isolated from murine endoplasmin showed significant homology (approximately 50%) with sequences in the heat-shock proteins 90 and 83 of yeast and Drosophila, respectively, indicating that they are related proteins. Mixed oligonucleotide probes, deduced from the peptide sequences, were used to isolate cDNAs from a murine liver cDNA library. DNA sequencing confirmed the presence of a coding sequence for one of the endoplasmin peptides, formally establishing the authenticity of the cDNA. The identity of the murine and hamster endoplasmin sequences suggests a level of sequence conservation associated with proteins that perform a structural role in cells.