There is a technique of engineering analysis which can be described as "impulse synthesis" which uses the observational data of a system's response to a single sharp blow in order to predict its response to a steady force. This same technique has been applied to the calculation of in situ drug levels and for calculating plasma clearance values. The purpose of this paper is to elucidate the principles of this calculation technique and to critically assess its application to plasma clearance studies. We begin by tracing the history of the measurement of renal clearance of plasma. We then proceed to exposit the relevant principles of the synthesis technique. Finally, we report the results of our application of this technique to the analysis of simulated data in a manner intended to be of use to clinicians who might wish to consider employing the technique.