This paper examines the potential of using methods derived from fuzzy set theory to utilize qualitative geological data in numerical modeling. An example application involving dynamic stratigraphic modeling is used to describe the basic design and function of a simple fuzzy system. Preliminary results, as well as advantages and limitations of a fuzzy approach to the problem of controlling sediment distribution in space and time, are discussed with reference to the example application. The potential of fuzzy logic in geological classification and prediction are briefly discussed, as are aspects on the robustness and objectiveness of fuzzy methods. The main conclusion is that, due to their ability to handle qualitative data and complex nonlinear relationships, fuzzy-logic-related methods are very well suited for using qualitative geological data in numerical models.