c-Rmil is the cellular allele of the v-Rmil oncogene, transduced during in vitro passaging of Rous associated virus type 1 in chicken embryonic neuroretina (NR) cells. The c-Rmil proto-oncogene is the avian homolog of the mammalian B-raf gene and belongs to the mil/raf oncogene family of serine/threonine protein kinases. We recently reported that the avian c-Rmil gene encodes two proteins of 94 and 95 kDa, resulting from an alternative splicing mechanism. We describe here the exon-intron organization of the coding region of the chicken c-Rmil locus. We show that c-Rmil proteins are encoded by 19 exons lying within about 100 kbp of genomic DNA. Comparison of the organization of this gene with those of the other mil/raf genes shows strong similarities within three conserved domains previously identified in mil/raf protein kinases. However, c-Rmil contains two additional 5' coding exons that are not present in the other mil/raf genes.