1. Four steers were used in thirty-five experiments each lasting 4–5 days in which the effects of variation in air velocity from 0·4 to 1·6 m.p.h. at environmental temperatures of 0°, 10° and 20°C. on heat production were studied using a respiration chamber. Measurements were made on animals with winter coats and in the same animals after shearing.
2. Standing time was increased by exposure to cold and slightly reduced by exposure to wind. The wind was so small that it had no effect on the measured coat depth. Piloerection increased winter coat depth by 30%. Heat production was increased by 17–20 kcal./hr. on standing.