The diplopodia-5 condition in fowl is caused by a single autosomal recessive lethal gene, dp-5, having complete penetrance and variable expressivity. Linkage tests with marker genes for naked neck, pea comb, rose comb, and dominant white were negative. A breeding test indicated that dp-5 and dp-3 are not allelic. Literature descriptions of dp-1, dp-2(extinct), and dp-4 (sex-linked) indicate that dp-5 differs from all of them. Diplopodia-5 embryos are tharacterized by extra digits on the preaxial side of the limbs, supernumerary metatarsal and metacarpal bones, shortened limbs and upper beak, reduced body weight and length, and inability to hatch.