Three clones carrying the sequences of ceruloplasmin gene were isolated from the library of EcoRI fragments of rat chromosomal DNA cloned in Charon 4A vector. These clones were identified using, i) plaque hybridization with [32P] cDNA transcribed from highly purified rat ceruloplasmin (Cp) mRNA; ii) blot hybridization of the restriction fragments of recombinant DNAs with Cp cDNA and iii) hybridization selection of Cp mRNA followed by its cell-free translation. Oligo (dT)-primed cDNA transcripts of Cp mRNA having different length as well as cloned Cp cDNA isolated from rat liver cDNA library were used as hybridization probes for the study of mRNA-coding segments of Cp gene. The length of inserts in recombinant DNAs varied from 7.5 up to 12.3 megadaltons. EcoRI-fragments of Cp gene were mapped within recombinant DNA and their homology to each other was studied.