The modelling basis of statistical moments in pharmacokinetics is cons
idered and the associated assumptions and restrictions highlighted. Bo
th deterministic and statistical models are described and they are see
n to give identical results on the basis of equivalent assumptions. It
is shown that it is not necessary to assume that all kinetic processe
s are first order and that some of the pharmacokinetic parameters may
be dependent on the dose of administered drug and on the route of admi
nistration.