A dosage of 3 mg Warfarin/kg body weight causes a highly significant increase in the number of platelets both in TMB (Tryon maze brights) and TMD (Tryon maze dulls) rats. Different "intelligence levels" show no effect on this increase. In condition of rest the number of platelets is significantly higher in TMD rats than in TMB animals. With regard to a hypothetical relationship between the number of platelets and the amount of circulating and urinary catecholamines the results suggest a similar relationship in conditions of rest as can be shown in emotive (e+) and nonemotive (e--) Wistar rats as well as a varying reaction to stress -- different levels of "intelligence" and anxiety provided.