A MARTINGALE APPROACH TO WEIGHTED APPROXIMATIONS David M. Mason University of Delaware A martingale approach to weighted approximations will be described. Special cases include the uniform empirical and quantile processes, the finite sampling process, the rank statistics process and the weighted bootstrap process. Special emphasis will be given to a weighted approximation to a serial rank type process from which the classical rank tests for serial correlation are formed. An unexpected random graph structure lurking behind serial ranks points the way to the necessary martingale. A number of applications to statistics will be discussed.