AbstractTHE derivation of the epithelium from which craniopharyngiomas arise is in doubt. Willis (1953) and Russell and Rubinstein (1959) state that these tumours are not distinguishable from “epitheliomas” in which squamous and basal cells are both present. Timperley (1968a), in a histochemical investigation, showed that craniopharyngiomas differed from squamous epithelium and epidermal cyst epithelium in that they contained a high activity of alkaline phosphatase and in this respect they closely resembled the ameloblastoma of the jaw and the developing tooth bud. The present paper is a histochemical and chemical analysis comparing several more craniopharyngiomas with dental and dentigerous cysts.