It was established that at increasing concentration of inhibitors (or activators) in the enzyme-substrate system the vector lengths of enzyme inhibition (and activation) retain a permanent tendency to increase, while the constants of enzyme inhibition (and activation) either remain unchangeable or change in any direction by studying the dependence of a course of change of vector length (li) and constants of enzyme inhibition (Ki) Examples are given of using the Ki constants and the vector lengths for the characterization of the strength of enzyme binding to inhibitor and the intensity of enzyme inhibition, respectively.