The intraosseous vascular anatomy of the radius was studied in 12 pairs of canine cadaver limbs. Six pairs of specimens were obtained from small-breed dogs (less than 6 kg) and six pairs were obtained from large-breed dogs (18 to 30 kg). All specimens were studied after arterial injection with India ink. Samples were fixed, frozen, then sectioned and processed using a modified Spalteholz technique. In all specimens, the intraosseous blood supply arose from the nutrient artery with its associated branches and the metaphyseal arteries. In small-breed dogs, there was decreased vascular density at the distal diaphyseal-metaphyseal junction compared with large-breed dogs. The reduced vascularity corresponded to the region associated with a poor prognosis for fracture healing in small-breed dogs. This regional association suggests that a decreased vascular supply in the distal radius may contribute to a higher frequency of delayed union and nonunion in smaller dogs.