This paper shows how to calculate solutions to Poisson's equation for
the waiting time sequence of the recurrent M/G/1 queue. The solutions
are used to construct martingales that permit us to study additive fun
ctionals associated with the waiting time sequence. These martingales
provide asymptotic expressions, for the mean of additive functionals,
that reflect dependence on the initial state of the process. In additi
on, we show how to explicitly calculate the scaling constants that app
ear in the central limit theorems for additive functionals of the wait
ing time sequence.