We have isolated several cDNA's complementary to gamma-glutamyltranspeptidase (GGT) mRNA by screening a rat kidney library constructed in lambda gtll with antibodies specifically reactive to the enzyme protein. The clone selected an mRNA that was translated into a 62 Kd peptide, corresponding to the GGT precursor. The longest clone isolated was 1842 bp long with an open reading frame coding for 565 amino acids. The length of the mRNA coding for GGT was estimated to be 2.2 kb long. The amino acid sequence derived from the nucleotide sequence matched the short sequences determined by us as well as by other authors.