Frequently, the clinical pharmacologist must call forth all of his ingenuity and clinical experience to design appropriate studies to be able to evaluate objectively the effectiveness of various sex steroids in man, particularly when the clinical appraisal is based on the patient's complaints rather than on a specific end point. The patient's subjective impressions may be so nebulous that the results of clinical investigations that are dependent upon them may be widely divergent. On the other hand, when more definitive and measurable effects of the steroid can be observed, the clinical evaluation may be accomplished in the same way as a doseresponse curve in animal studies. However, even when quantitative analyses may be applied, variable results may be noted because of differences in techniques and marked biologic variations. Inconsistencies in the activity of a steroid may be observed in different laboratories even though the same preparations and doses are used. It should be emphaSized that while laboratory procedures may be used in drug evaluation, they do not automatically confer precision upon the analyses, particularly when the activity that is being analyzed may merely represent a rough measure of biologic activity or degradation.