Human proproacrosin is specified by a single gene (ACR). Using a series of human-rodent somatic cell hybrids containing variant complements of human chromosomes, the preproacrosin gene was found to cosegregate with human chromosome 22. Somatic cell hybrids containing translocation chromosomes carrying parts of chromosome 22 were used to locate the preproacrosin gene to the region 22q13-22qter. By probing the DNA of 82 individuals, a restriction fragment length polymorphism was found with SstI in 14 cases.