The term "brain fever" is often applied clinically to individuals suffering recurrent and at times hectic courses of fever and who are known to have had excessive damage to the brain. Few documented reports of this condition have appeared in the literature to support the concept. The authors provide detailed study of two children with cerebral palsy who exhibited prolonged episodes of fever which could not be accounted for by any disease process other than the fixed lesion in the brain. The authors discuss the relationship between the tendency towards such episodes of fever and areas within the brain which have been found to be damaged. The authors consider that this so-called cerebral fever may arise from a disturbed thermal regulation, resulting from lesions in the hypothalamus or from lesions elsewhere in the brain.