This paper, the last in a four part introduction to geostatistics, describes the application of simulation to site investigation problems. Geostatistical simulation is a method for generating digital representations or “maps” of a variable that are consistent with its values at sampled locations and with its in situ spatial variability, as characterized by histogram and variogram models. Continuing the synthetic case study of the three previous papers, the reader is lead through the steps of a geostatistical simulation. The simulated fields are then compared with the exhaustive data sets describing the synthetic site. Finally, it is shown how simulated fields can be used to answer questions concerning alternative site remediation strategies.