Many empirical and theoretical CPT interpretation methods are broadly accepted and used in practice. These approaches tend to consider whether the cone penetration is drained or undrained, and then will consider the soil as either “sand” or “clay,” respectively. Most fundamental research into the CPT and its interpretation considers penetration through sands or clays separately, and includes verification tests in materials with close to ideal sand or clay behavior. However, in our engineering practice over the past five years, we have encountered several instances where the soils are not typical and the usual methodologies are inadequate or lead to inconsistent conclusions. This paper describes three of these case histories and our approach to using the CPT in each case.