Yao is a Bantu language spoken by about 100,000 people in Southern Tanganyika; by nearly a third of a million people in Nyasaland, and by a much larger but unspecified number in Portuguese East Africa. Grammatical studies of the language as spoken in Nyasaland have been made by Sanderson (1922) and Hetherwick (1902), and Sanderson's Dictionary appeared in 1954. Anthropologically the Nyasaland Yao have been intensively studied by Professor J. C. Mitchell, but the Tanganyika section has remained largely unstudied, either by linguists or anthropologists.