Ribonuclease/angiogenin inhibitor (RAI) is a tight-binding inhibitor of ribonucleolytic and angiogenic activities involved in tumor progression. It is translated from various mRNAs differing in their 5 regions and originating from a single gene locus. Recently, this gene (RNH) has been assigned to 11p15.5, the terminal part of the short arm of chromosome 11. The regional chromosomal localization was confirmed by somatic cell and in situ hybridization and further refined by long-range restriction mapping. The data place RNH within 90 kb of the Harvey-ras protooncogene (HRAS), so far the most telomeric gene on 11p, in a region involved in growth regulation and tumor development.