The palmomental reflex was elicited, unilaterally or bilaterally, in 28% of a series of 121 patients with neurological disorders. There was no significant variation in the prevalence of the palmomental reflex with the age and the sex of patients, with the cause of the neurological disorder, or with the site of cerebral lesions. However, the reflex was found to be significantly more common among patients with signs of focal or generalized brain dysfunction than among patients with normal cerebral function (P less than 0.001). The side of the body on which the reflex was elicited was no indication of the side on which the cerebral lesion was situated. In three patients, who were examined on several occasions, the reflex disappeared as the psychomotor function of the patients improved. On the basis of the results, the nature of the palmomental reflex and the reasons why its presence is difficult to interpret are discussed.