For evanescent Markov processes with a single transient
communicating class, it is often of interest to examine the limiting
probabilities that the process resides in the various transient states,
conditional on absorption not having taken place. Such distributions are known
as quasi-stationary (or limiting-conditional) distributions. In this paper we
consider the determination of the quasi-stationary distribution of a general
level-independent quasi-birth-and-death process (QBD). This distribution is
shown to have a form analogous to the matrix-geometric form possessed by the
stationary distribution of a positive recurrent QBD. We provide an algorithm
for the explicit computation of the quasi-stationary distribution.