The theory of the mean first passage time is developed for a general discrete nonMarkov process whose time evolution is governed by a generalized master equation. The mean first passage time is determined by an adjoint matrix f~+ in a form analogous to the Fokker Planck case. The theory is illustrated by two examples: A onedimensional unit step non-Markov process and a non-Markov process with two-step transitions. Explicit expressions for the mean first passage time are derived.