We derive the MacLaurin series for the moments of the system time and
the delay with respect to the parameters in the service time or intera
rrival time distributions in the GI/G/1 queue. The coefficients in the
se series are expressed in terms of the derivatives of the interarriva
l time density function evaluated at zero and the moments of the servi
ce time distribution, which can be easily calculated through a simple
recursive procedure. The light traffic derivatives can be obtained fro
m these series. For the M/G/1 queue, we are able to recover the formul
as for the moments of the system time and the delay, including the Pol
laczek-Khinchin mean-value formula.