The simultaneous occurrence of factor XII deficiency and von Willebrand's disease (VWD) is described in a family of Miniature Poodles affected concurrently with a familial non-spherocytic hemolytic anemia. Although there was a dominant distribution of factor XII deficiency in this family of dogs, only the dogs suffering from non-spherocytic hemolytic anemia had concurrent VWD gene expression. Neither the factor XII deficient dogs nor the VWD carrier dogs displayed bleeding tendencies.