Based on the sequence of the human endothelin-1-converting enzyme (hECE-1) cDNA, we cloned a 1982 bp cDNA fragment and we amplified by PCR a 3' fragment located on the last exon (exon 19). Human metaphase chromosomes were studied by Fluorescent in Situ Hybridization (FISH) using the 1982 digoxigenated hECE-1 fragment as a probe and chromosome 1-specific probes. Twin spot signals on each of the two homologous chromosomes 1 were found by FISH on band p36. The results of monochromosomal hybrids confirmed that hECE-1 is on chromosome 1. Radiation hybrid mapping localized the hECE-1 gene 3.15 cR far from D1S2436 (WI-3177), at about 25 cM from the telomere of the short arm, possibly at the border between 1p36.3 and 1p36.2.