A model of bleeding due to clotting factor deficiency has been developed in dogs. Normal and hemophilic (factor VIII:C deficient) animals were used. Bleeding was induced in lightly anesthetized animals by severing the apex of the nail cuticle using a guillotine device. In normal animals, bleeding usually ceased spontaneously after 2–8 min. In contrast, in hemophilic animals, bleeding continued for up to 20 min and necessitated either cauterization or the application of topical thrombin to achieve hemostasis. Pretreatment of the hemophilic animals with canine cryoprecipitate corrected the cuticle bleeding time to within the range noted for normal animals. The method is simple and reproducible and has the advantage that a number of observations can be made sequentially on the same animal. Rebleeding of the cauterized cuticle of the hemophilic animals did not usually occur. This model has considerable potential for the preclinical testing of products considered to bypass or replace factor VIII:C in patients with acquired inhibitors of factor VIII:C and may be adapted to the study of other mechanisms involved in normal and abnormal hemostasis.