Sheep liver cytosolic aldehyde dehydrogenase (AIDH) has been studied extensively by others from this department (reviewed in Blackwell et al., 1989). In order to extend these studies using site-directed mutagenesis it was necessary first to isolate and sequence the cDNA for this form of the enzyme. The cDNA sequences for the human liver cytosolic (Hsu et al., 1989) and mitochondrial iso-forms of AIDH (Hsu et al., 1988) were used to design a probe which would allow specific identification of cytosolic AIDH. We report here the isolation and sequencing of a full-length clone for sheep liver cytosolic AIDH.