Members of the genus live in the Thai-Malay Peninsula, on Sumatra, Borneo, Java and smaller nearby islands.

They differ from the other langurs by characteristics in the shape of their head (particularly the poorly developed or absent brow ridges, and the prominent nasal bones),[2] in the teeth, and by the size of their small thumbs.

[3] A few species have been observed in monogamous pairings (particularly the Mentawai langur),[3] although this might be a reaction to the decrease of their habitat.

Newborn animals are white colored and have a black strip at the back, although some have a cross-shaped mark.

The typical life expectancy in the wild remains poorly known for most species, but captive Sumatran surilis have lived more than 18 years.

[2] Several species in this genus are restricted to regions with extensive habitat destruction, and are also threatened by hunting.

Consequently, 16 of the 19 species are rated as vulnerable or worse by IUCN,[4] and the Sarawak surili has been referred to as "one of the rarest primates in the world.

"[5] Recently, a subspecies of Hose's langur called Miller's grizzled langur, thought to be extinct, was rediscovered in the Wehea Forest on the eastern tip of Borneo island,[6] though it remains one of the world's most endangered primates.