The joint probability density function of the state space vector of a
white noise excited van der Pol oscillator satisfies a Fokker-Planck-K
olmogorov (FPK) equation. The paper describes a numerical procedure fo
r solving the transient FPK equation based on the path integral soluti
on (PIS) technique. It is shown that by combining the PIS with a cubic
B-spline interpolation method, numerical solution algorithms can be i
mplemented giving solutions of the FPK equation that can be made accur
ate down to very low probability levels. The method is illustrated by
application to two specific examples of a van der Pol oscillator.