In India, the capped langur (Trachypithecus pileatus) occurs in Assam, Arunachal Pradesh, Manipur, Meghalaya, Mizoram, Nagaland, and Tripura. Elsewhere it is found in Bhutan, Bangladesh, northwestern Myanmar and a small area of Tibet, China. It is a forest-dwelling primate occurring in lowland, wet, evergreen rain forest to temperate forest. It ranges from the plains, 5 m above sea level, to 2,800 m in the Himalaya. Although it is the second most abundant primate of Assam, its populations are declining due to continuous destruction of its forests, and also hunting. Since the 1980s, one-third of the capped langur habitat in Assam has been lost because of tree felling and encroachment. It has been recorded in 53 protected areas in Northeast India. Of five subspecies recognized in the past (pileatus, durga, brahma, shortridgei and tenebricus) shortridgei is now considered to be a full species, and durga a junior synonym of pileatus. Trachypithecus p. pileatus occurs south of the Brahmaputra River; T. p. brahma and T. p. tenebricus occur north of the river. The lower reaches of the Jia-Bhoreli—Kameng River separate tenebricus (in the west) from brahma (in the east), but in the upper reaches in the higher Himalaya there is possible intergradation. Here, I report on hitherto unrecorded differences in facial hair patterns, (especially the cap) that differentiate the three subspecies. The langurs south of the Brahmaputra (pileatus) have shorter whiskers, and a distinct, conspicuous “army-cut hairstyle”-like cap, well separated from the ears. The subspecies to the north can be separated by the form of the cap—hairs radiating from the forehead to form a shaggy cap in tenebricus, and a less shaggy cap, resembling that of pileatus, but which extends to the ears in brahma. The distinguishing features are more dependable than overall color patterns, which vary individually and with age, sex, and season.