Some taxonomies divide Sino-Tibetan into Sinitic and Tibeto-Burman branches (e.g. Benedict, Matisoff). However, other scholars deny that Tibeto-Burman comprises a monophyletic group. Van Driem argues that the Sino-Tibetan family should be called "Tibeto-Burman", but this usage has not been widely adopted. Others exclude a relationship with Chinese altogether (e.g. Beckwith, R. A. Miller).
During the 18th century, several scholars noticed parallels between Tibetan and Burmese, both languages with extensive literary traditions. In the following century, Brian Houghton Hodgson collected a wealth of data on the non-literary languages of the Himalayas and northeast India, noting that many of these were related to Tibetan and Burmese. Others identified related languages in the highlands of south-east Asia and south-west China. The name "Tibeto-Burman" was first applied to this group in 1856 by James Logan, who added Karen in 1858. Charles Forbes viewed the family as uniting the Gangetic and Lohitic branches of Max Müller's Turanian, a huge family consisting of all the Eurasian languages except the Semitic, "Aryan" (Indo-European) and Chinese languages. The third volume of the Linguistic Survey of India was devoted to the Tibeto-Burman languages of British India.
Julius Klaproth had noted in 1823 that Burmese, Tibetan and Chinese all shared common basic vocabulary, but that Thai, Mon and Vietnamese were quite different. Several authors, including Ernst Kuhn in 1883 and August Conrady in 1896, described an "Indo-Chinese" family consisting of two branches, Tibeto-Burman and Chinese-Siamese. The Tai languages were included on the basis of vocabulary and typological features shared with Chinese. Jean Przyluski introduced the term sino-tibétain (Sino-Tibetan) as the title of his chapter on the group in Antoine Meillet and Marcel Cohen's Les Langues du Monde in 1924.
The Tai languages have not been included in most Western accounts of Sino-Tibetan since the Second World War, though many Chinese linguists still include them. The link to Chinese is now accepted by most linguists, with a few exceptions such as Roy Andrew Miller and Christopher Beckwith. More recent controversy has centred on the proposed primary branching of Sino-Tibetan into Chinese and Tibeto-Burman subgroups. In spite of the popularity of this classification, first proposed by Kuhn and Conrady, and also promoted by Paul Benedict (1972) and later James Matisoff, Tibeto-Burman has not been demonstrated to be a valid family in its own right.
Most of the Tibeto-Burman languages are spoken in inaccessible mountain areas and many are unwritten, which has greatly hampered their study. It is generally much easier to identify a language as Tibeto-Burman than to determine its precise relationship with other languages of the group. The subgroupings that have been established with certainty number several dozens, ranging from well-studied groups of dozens of languages with millions of speakers to several isolates, some only newly discovered but in danger of extinction. These subgroups are here surveyed on a geographical basis.
The southernmost group are the Karen languages, spoken by three million people on both sides of the Burma–Thailand border. They differ from all other Tibeto-Burman languages (except Bai) in having a subject–verb–object word order, attributed to contact with Tai–Kadai and Austroasiatic languages.
The most widely spoken Tibeto-Burman language is Burmese, the national language of Myanmar, with over 32 million speakers and a literary tradition dating from the early 12th century. It is one of the Lolo-Burmese languages, an intensively studied and well-defined group comprising approximately 100 languages spoken in Myanmar and the highlands of Thailand, Laos, Vietnam and Southwest China. Major languages include the Loloish languages, with two million speakers in western Sichuan and northern Yunnan, the Akha language and Hani languages, with two million speakers in southern Yunnan, eastern Myanmar, Laos and Vietnam, and Lisu and Lahu in Yunnan, northern Myanmar and northern Thailand. All languages of the Loloish subgroup show significant Austroasiatic influence. The Pai-lang songs, transcribed in Chinese characters in the 1st century, appear to record words from a Lolo-Burmese language, but arranged in Chinese order.