The tail asymptotics of the distribution of the waiting-time W in some
polling models is investigated. When this is of the form P[W > x] sim
ilar to alpha x(beta)e(-eta x) for some alpha, beta, eta, we show how
to calculate the exponents beta and eta, and we establish the extent a
nd form of their dependence on the distributions of the service-time a
nd switchover-time. The exponents are expressed in terms of the fixed
points and Lyapunov exponents of a dynamical system which we associate
with the recursion which is used to calculate the moment generating f
unctions of the waiting time.