A clone coding for beta-lactoglobulin A has been isolated from a cDNA bank constructed from poly(A+)mRNA isolated from the bovine mammary gland. Its nucleotide sequence codes for the beta-lactoglobulin A, from amino acid residues Leu-11 to Ile-162, as based on the amino acid sequence reported by Braunitzer et al. [Z. Physiol. Chem. 354 (1973) 867-878]. In addition to the 455-bp coding sequence, our clone pB beta L4-10 contains a 3'-nontranslated region of approx. 270 bp.