Residual mapping is an automated groundwater-model calibration technique which rapidly identifies parameter-zone configurations, while limiting tendencies to over-parameterize. Residual mapping analyzes the model residual, or the difference between model-calculated head and spatially-interpolated observation data, for non-random trends. These trends are entered in the model as parameter zones. The values of hydrologic variables in each parameter zone are then optimized, using parameter-estimation software. Statistics calculated by the parameter-estimation software are used to determine the statistical significance of the parameter zones. If the parameter-value ranges for adjacent zones do not have significant overlap, the zones are considered to be valid. This technique was applied to a finite-difference, transient groundwater flow model of a major municipal well field, located in west-central Florida. A computer conde automates the residual mapping process, making it practical for application to large, transient flow models. The calibration data set includes head values from 37 monitor wells over a period of 181 days, including a 96-day well-field scale aquifer-performance test. The transient residual-mapping technique identified five significant transmissivity zones and one leakance zone.