For example, a well known textbook first presents both the classical integrated rate Eqn (1) and the tight-binding rate Eqn (4) in an introductory section entitled "Determining k obs : The Rate Constant for Onset of Inhibition". Here the reader is correctly informed that in the absence of tight-binding we are allowed to use the simpler Eqn (1) to determine k obs values, whereas in the presence of tight-binding we must use the more complex Eqn (4). In a subsequent section, entitled "Determination of Mechanism and Assessment of True Affinity", the book then proceeds to discuss how to differentiate between the onestep Mechanism A and the two-step Mechanism B based on the concentration dependence (linear or hyperbolic) of k obs values. Unfortunately, this particular choice of sequencing the mathematical material can create a false impression among some readers that k obs values determined either from Eqn (1) or from Eqn (4) can be used for mechanism discrimination in this particular manner. In fact, over the years, this investigator has encountered several internal reports and slide presentations, circulating inside various drug discovery establishments, where just such a misconception existed after exposure to the textbook in question . One goal of this report was to present a clarification of this complex mathematical issue.