We have characterized the structure of a mouse bone morphogenetic protein (BMP) type I receptor gene that can bind both BMP-2 and BMP-4. The mouse BMP-2/4 receptor gene is encoded by 11 exons and spans approximately 38-kb. Most of the intron/exon boundaries are not conserved compared to the kinase domain of the related, activin type II receptor. In addition, whereas the activin type II receptor gene contains large introns (> 40 kb), the largest intron of the BMP-2/4 receptor gene is only 6.4-kb. The BMP-2/4 receptor gene (Bmpr) was mapped to mouse chromosome 14. Bmpr is closely linked to Rbp3 in the region containing pugnose, a mutation that alters bone development. Knowledge of the genomic structure of Bmpr provides important information to create Bmpr-deficient mice.