Objective statistical evaluation of the results of experiments designed to measure the dissociation constants of stimulant drugs is discussed. A logistic function is fitted to the control dose-response curve to get control concentrations corresponding to concentrations in a second curve. The resulting pairs of concentrations are then compared with the appropriate theoretical model. This comparison proves to be most appropriately done by fitting a hyperbola directly to the data rather than by the conventional method of fitting a line to a reciprocal transformation of the data. The mechanics of the calculations are given in an appendix.