This essay reviews the functions of the Tanzanian National Central Library (NCL) and evaluates the activities performed and services provided by the NCL in light of the definitions of national library functions established by UNESCO and by K. W. Humphreys, Librarian of the University of Birmingham. The relationship between the NCL and the Tanzanian Library Service is outlined and the national library movement in the developing countries of Africa is described. A list of the administrative and accounting, technical and reader, consultancy and advisory, and book production services performed by the NCL is incorporated in the text. Two charts, the first comparing the UNESCO definition of a national library with the functions of the NCL, and the second comparing Humphreys' list of national library functions with the functions of the NCL, are also included. A checklist of national library functions and a 20-item reference list accompany the essay. (JL)