SUMMARYActivated coagulation time, one stage prothrombin time and activated partial thromboplastin time were compared in warfarin‐intoxicated dogs. All coagulation tests were significantly prolonged on the third and fourth days following intoxication. Coagulation assays of all dogs except one returned to preintoxication values one day following vitamin K therapy. Significant correlation was found between all coagulation tests in the intoxicated group. Activated coagulation time may provide a useful coagulation screening test to veterinarians with limited laboratory capabilitie