We constructed a complementary DNA (cDNA) library from Baikal omul (Coregonus autumnalis migratorius Georgi) pituitary glands. Synthetic oligonucleotide probes corresponding to chum salmon prolactin (PRL) cDNA were used to select the recombinant plasmids carrying the omul PRL gene. The larger insert was sequenced and found to encode a polypeptide of 210 amino acid residues, including a putative signal sequence of 23 amino acids. Nucleotide and predicted amino acid sequence of omul PRL showed high homology with other salmonid PRLs.