Modeling water movement in the unsaturated zone requires a great number of parameters, such as the initial water content, the saturated moisture content, and the saturated hydraulic conductivity, which can relatively easily be assessed. Other functions such as the suction head and the relative hydraulic conductivity, which are highly nonlinear functions of the actual water content are more difficult to find. Furthermore, infiltration experiments carried out at a few locations can only define these parameters at selected locations, and a reasonable interpolation of these parameters is extremely difficult. In this paper, two fuzzy logic-based models are presented for the infiltration process. Basic definitions of fuzzy sets are given, and basic operations are explained. Principles of the rule-based infiltration models are presented. The rules for the first model are based on the moisture content of the adjacent layers and the depth of the wetting front. Using these rules, the flows can be calculated as exact quantities. The rules are derived from a training set which was obtained from several test runs of a Green and Ampt (GA) infiltration model. Separate rules are derived for the flow dynamics in the upper layer (runoff and infiltration), and for water flow between the layers. Examples of the application of the model are given. The model performs with similar accuracy as the GA model, using only 40% of its parameters and running 2 orders of magnitude faster. A training set obtained by numerical solution of the Richards equation was used to create a second fuzzy rule-based model. Here the rules are based on the moisture content of the adjacent layers. Results obtained by the use of the models are compared with measured values, showing a very accurate reproduction of the values. ¿ American Geophysical Union 1993