A 5' fragment of a full-length cDNA clone encoding a human phenol UDP-glucuronosyltransferase was used to produce a specific probe for this gene. DNA isolated from a panel of 18 human-rodent somatic cell hybrids was analysed by Southern-blot hybridization. The results indicate that this UDP-glucuronosyltransferase is encoded by a single gene, designated GNT1, located on human chromosome 2.