  We introduce a rate balance principle for general (not necessarily Markovian)
stochastic processes. Special attention is given to processes with birth and
death like transitions, for which it is shown that for any state $i$, the rate
of two consecutive transitions from $i-1$ to $i+1$, coincides with the
corresponding rate from $i+1$ to $i-1$. This observation appears to be useful
in deriving well-known, as well as new, results for the Mn/Gn/1 and G/Mn/1
queueing systems, such as a recursion on the conditional distributions of the
residual service times (in the former model) and of the residual inter-arrival
times (in the latter one), given the queue length.
