ABSTRACTThrough the years the Theis equation has played an important role in ground‐water hydrology. Comparison of experimental pumping‐test data with this theoretical curve by graphic means has been a standard method of determining aquifer transmissivity and storage. The purpose of this paper is to present a technique and an algorithm to automatically fit experimental pumping‐test data to the Theis equation by obtaining the “best” transmissivity and storage in the least squares sense through the use of sensitivity analysis. The automated fit for pumping‐test data developed in this work should be a useful tool for the ground‐water hydrologist. Use of the technique is simple, quick, and inexpensive, and has the advantage of always being objective. As a measure of the error in fitting, the rms deviation in drawdown is calculated for the “best” transmiss