The interferon-inducible double-stranded RNA-specific adenosine deaminase is an RNA-modifying enzyme implicated in the generation of biased hypermutations viral RNAs and the site-selective editing of mammalian mRNAs of neural origin. The gene for the dsRNA-specific adenosine deaminase has been mapped by fluorescence in situ hybridization (FISH) of genomic clones to a single locus on human chromosome 1 bands q21.1-21.2. Simultaneous multicolor FISH including lambda clones and yeast artificial chromosomes showed a localization of the gene in band 1q21 centromeric of D1S1705.