This description of the phonology, morphology and syntax of the endangered (Tibeto-Burman) Jero language as spoken in eastern Nepal, appears in sequel to the author’s 2004 Grammar of Wambule, the language most closely related to Jero. It pictures the complex-pronominalising language of the Jero Rai, one of the Kiranti tribes of eastern Nepal. With a historical comparative study of the Kiranti languages, the branch of the Tibeto-Burman language family to which both Jero and Wambule belong. An exhaustive and model reference work for Tibeto-Burman linguistics, language typology and linguistic theory. With financial support of the International Institute for Asian Studies.