Two different genomic clones containing the entire coding sequence of human glucocerebrosidase were isolated from a fetal liver library using a cDNA probe previously cloned by us. These clones correspond to two human glucocerebrosidase genes, designated 6-1 and 10-2. Clone 6-1 contains sequences homologous to the cDNA we cloned previously. The promoter regions of the genes were identified by S1 analysis and sequenced. They contain TATA- and CAAT-like boxes, but lack a GGCGGG motif. When coupled to the bacterial gene coding for chloramphenicol acetyl transferase (CAT) and transfected to Gaucher skin fibroblast lines, both promoter fragments enhanced CAT activity. The promoter of gene 6-1 was eight times more efficient than the promoter of gene 10-2. Northern blot analysis revealed three human glucocerebrosidase RNA species of 6, 2.6, and 2.2 kb in size. The 6-kb transcript is probably a nuclear transcript whereas the 2.6-kb and 2.2-kb transcripts are cytoplasmic species which emerge from polyadenylation at different sites.