The operational and conceptual significance of the reactor kinetics parameters is considered, with especial reference to the generation time, the reciprocal production probability. The kinetics equations are given in a form parametric in the generation time, a form which is usually more accurate and always simpler to solve than the corresponding form in the lifetime, the reciprocal destruction probability. Typical solutions are given for several simple and more sophisticated problems employing a further useful set of nondimensional parameters.