Some 350 surgical specimens obtained at partial or total laryngectomy were photographed immediately after operation and processed for study by serial section. Intralaryngeal barriers to the spread of cancer are demonstrated on one hand and pathways of infiltration and destruction on the other. The following conclusions are based on these studies: two major elastic tissue barriers that influence the spread of vocal cord cancer are the dense mass of connective tissue at the anterior commissure which prevents invasion of the thyroid cartilage until very late, and the conus elasticus, under which vocal cord cancer may advance subglottically under the intact overlying mucosa. This conceals the actual extent of cancer below the glottis and is the usual cause of local recurrence after hemilaryngectomy. A large subglottic component of a glottic or transglottic cancer is sometimes associated with extension of disease within the cancellous interior of the thyroid ala or cricoid ring under an intact mucosa. A large ventricle or saccule may harbor the bulk of a glottic cancer under an intact ventricular band. Hemilaryngectomy is usually contraindicated once the extent of such a tumor is recognized. Removal of the hyoid bone is rarely necessary at horizontal supraglottic partial laryngectomy. Its preservation facilitates postoperative deglutition. Partial laryngectomy should not be attempted for pyriform sinus cancer if inspection reveals involvement of the apex.