Insulin-degrading enzyme (IDE) is a cytosolic proteinase involved in the cellular processing of insulin. Using somatic cell hybrid analysis and in situ chromosomal hybridization, we have localized the gene encoding IDE to human chromosome 10, bands q23----q25. The murine Ide gene was previously mapped to Chromosome 19; together, these results suggest that the IDE gene is a member of a conserved syntenic group on human chromosome 10, bands q23----q25 and mouse Chromosome 19.