We have cloned and sequenced the rat Bmyc gene. The rat Bmyc gene contains sequences related to the central part of c-myc, namely the first intron, the second exon, and the noncoding part of the third exon. The homology drops in the 3' part of the c-myc second exon, but continues in the noncoding part of the third exon. We have sequenced the total predicted coding region of the Bmyc. The longest open reading frame in Bmyc suggests a protein of 178 amino acids, which is only 41% of the c-myc protein size. To confirm the putative open reading frame, we have produced a trpE-Bmyc protein that is detected with a pan-myc antibody. We discuss these findings in the context of potential functional domains and the possibility of overlapping and distinct activities of myc-family proteins.