Oral glands underwent substantial modification during the origin and diversification of snakes. Oral glands have provided rich data for snake systematics, and for informing evolutionary scenarios about the adaptive radiation of snake feeding. However, sampling has been patchy, and many questions remain about gland homology, function and evolution. This chapter addresses labial (supra- and infralabial), temporomandibular, rictal, sublingual, premaxillary, accessory and dental (= venom and Duvernoy’s) glands. We review and synthesize developments and data and present new histological sections and high-resolution tomography of some snakes and lizards, providing descriptions and illustrations of oral glands and associated structures. We comment on labial and dental glands of some toxicoferan and non-toxicoferan lizards, and report the first observation of a possible infralabial gland in a dibamian lizard. There are insufficient data to resolve all outstanding questions about gland homology across lizards and snakes, but the ancestral snake possibly had rictal and lacked dental (venom) glands, the latter perhaps evolving only within colubroidean caenophidians.