1. Sodium warfarin, given by oral or by parenteral route, displays a pronounced anti-inflammatory effect in the formaldehyde and carrageenan induced rat paw edema. This effect becomes patent not only when the warfarin application precedes the local injection of the irritant substance (prophylactic effect), but also when it is given to animals with already developed inflammatory reactions (therapeutic effect). 2. The active doses of Na warfarin lie between 0.5 and 5.0 mg/kg. Smaller as well as higher doses show a reduced anti-inflammatory effect. 3. A marked anti-inflammatory effect can be noted already 90 min after drug injection at a still normal prothrombin level. 4. Vitamin K1 (phylloquinone), given by oral or parenteral route, in doses from 1.6 mg/kg upwards, shows a marked anti-inflammatory effect both in the prophylactic and the therapeutic rat paw test. Vitamin K3 is devoid of any anti-inflammatory activity. 5. The anti-inflammatory effect of both sodium warfarin and of vitamin K1 in rats, is not interfered with by previous adrenalectomy.