S the most common cancer affecting the human body. This tumor prototype may originate in more anatomical sites than any other form of carcinoma, since it is the usual cancer of the skin, lip, oral cavity, pharynx, larynx, bronchi, esophagus, anus, vulva, vagina, cervix, urethra, penis, and even bladder and renal pelvis. Rarely, it may occur primarily or as a metaplastic variant in other organs. Since the behavior patterns of this morphological entity would seem to have many similar characteristics in its differing locations and microscopic variations, detailed knowledge of the natural history of this disease is of some importance. As our most readily available source of squamous-cell carcinoma, oral cancers were studied from the standpoint of their origins and manner of spread. Tumors of the lip, oral cavity, and pharynx in 783 patients have been reviewed, with findings that reinforce the concept of multifocal growth of these tumors. The mu1 ticen tric origin of epidermoid carcinoma is not widely accepted, although such occurrence in the skin is generally recognized and studies of in situ carcinoma of the cervix uteri are indicative of this origin.