Two patients with unilateral facial hyperhidrosis, a rare disorder of the sweat glands, are described. Employing thermal and carbachol stimulation tests, the functional status of sweat glands on the affected sites were studied. A marked increase in sweat gland activity was noted on the affected areas as compared to the contralateral normal sites. The histological examination of the affected skin revealed considerable enlargement of the sweat glands with dilatation of the sweat ducts and an intense mononuclear infiltrate in the periductal area. The epidermis, at places, showed spongiform vesiculation invaded by an identical inflammatory infiltrate. The striking histological resemblance of this condition to the dyshidrotic eruption commonly encountered on the hands and the feet is stressed.