The manual is a practical self study guide illustrating the application of the USGS modular ground-water flow model, MODFLOW. It was developed as a text for modeling and ground-water hydrology courses and as a self study guide to aid regulators, modelers, and educators in learning MODFLOW. The information in the manual should be of interest to both the beginner and advanced modeler for hands-on experience with the practical application of MODFLOW. In addition, the problems in the manual can be used to verify the correct installation of the MODFLOW code on a particular computer system as a benchmark for the verification of other flow models. The text introduces each problem, describes the available input data, outlines the output, and discusses the results. Each problem is supported by several figures and tables to illustrate and clarify the model scenario. The diskettes contain input and output data sets for each problem. A copy of MODFLOW is not included in the manual. It is assumed the user has obtained a copy of MODFLOW and has the necessary computer hardware to execute the program.