1. The pattern and control of sweating in one breed of goat and six breeds of sheep have been studied.2. Heat exposure of both sheep and goats resulted in periodic discharges of moisture on to the surface of the skin of the shorn mid-side. The frequency of discharge showed considerable variation between individual animals, varying from less than 1/hr to 14/hr. Approximate counts of the number of active sweat glands suggested that the same glands were involved at each discharge.3. The amount of moisture produced at each discharge declined upon continued heat exposure. The rate of decline was independent of the frequency of discharge.4. Adreno-medullary denervation had no effect on the pattern of sweating in either the sheep or the goat.5. Intravenous adrenaline administration (5 mug/kg body wt.) caused the sweat glands to discharge, but noradrenaline had no effect at the same dose.6. Thermal sweating was inhibited by bethanidine and phenoxybenzamine but not by propranolol. Sweating induced by intravenous adrenaline administration was blocked by phenoxybenzamine but not by bethanidine or propranolol.7. It is concluded that sweating on the mid-side of the sheep and goat is controlled by an adrenergic mechanism, that secretion from the adrenal medulla under conditions of mild heat stress does not stimulate the glands and that sweating is mediated by adrenergic alpha-receptors.