THE SALIVARY GLANDS of about 180 species, rep-resenting some 120 genera, of snakes were examined histologically, those of 71 genera for the first time. The supralabial and glands of Duvernoy are described, and the intraspecific variation within these glands is summarized on the basis of a computer analysis. The patterns of the similarity matrices were compared with the phylogenetic schemes pro-posed by various authors for the Colubridae. The conclusions reached are as follows. There is a trend toward the reduction of cell height with the development of a large Duvernoy’s gland. Duvernoy’s glands in the Natricinae seem to be characterized by mucous cells. The Xenoderminae have a unique arrangement of the supralabial glands, with an alternation of serous- and mucous-cell cords along the supra-labial ridge. Duvernoy’s glands in the Homolopsinae form a gradually enlarging series, with the largest glands found in Enhydris. The variation of the histological pattern in the Duvernoy’s glands of the Colubridae clearly op-poses the view that the Boiginae (Dipsadomor-phinae of authors) are a natural group. The varia-tion of pattern within the Colubrinae and the Boiginae is so great and the overlap so complete that no difference can be seen in the labial glands of the Colubridae that would support the separa-tion of the Boiginae from the Colubridae in respect to this character. The gland in Dispholidus typus is different from the other colubrid glands examined and can be readily differentiated from all other glands.