The molecular identities of most volume-regulated ion channel proteins and putative regulatory elements are currently unknown. Recently, a role for a nucleotide-sensitive chloride conductance regulator, ICln, in the function of a ubiquitous volume-regulated chloride channel has been suggested. Here, we report the cloning of a fragment of the mouse Icln gene and identification of probable Icln pseudogenes. The functional Icln gene was mapped independently to human chromosome 11q13.5-q14 and mouse chromosome 7 (50.3 cM). ICln mRNA was shown to be abundantly expressed and evenly distributed in all mouse tissues examined and at four stages of embryonic development, consistent with the proposed role of ICln in the regulation of a ubiquitous chloride channel.