1. Arterial and venous reactions in forearm and hand to a deep breath or to mental strain (a 50 s period of arithmetic) were measured in fourteen individuals. Blood flow and tissue volume change were measured by venous occlusion plethysmography, and venous tone by the occluded limb technique.
2. A deep breath caused cutaneous vasoconstriction which was short-lasting in resistance (arterial) vessels and long-lasting in capacitance vessels.
3. Mental strain caused cutaneous venous constriction and muscular arterial dilatation with a similar time-course, while the cutaneous arterial reaction was variable.