The us of healthy volunteers is essential to drug development. Studies of safety, drug metabolism, and pharmacokinetics are best conducted in subjects without the added interpretive complications introduced by the presence of disease. In this study, medical findings for 135 prisoners and 54 student volunteers were evaluated. Admission to both studies was restricted to males between the ages of 18 and 45. The screening program included laboratory work consisting of complete blood count, urinalysis, serum glucose, blood urea nitrogen, alkaline phosphatase, lactic dehydrogenase, serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase, and total bilirubin. Electrocardiograms, physical examinations, and medical history questionnaires were administered to those subjects who passed the initial laboratory screening procedures. A similar sequence of testing was followed with the 54 student volunteers. Based upon the screening procedures, 34 prisoners were eliminated as acceptable candidates for medical reasons, and 11 were eliminated for nonmedical reasons. A total of 24 students were eliminated for medical reasons and none was eliminated for nonmedical reasons. It is suggested that in future screenings only the most pertinent tests be included, such as urinalysis, electrocardiogram, and hematocrit. In addition, it is apparent from the study that prisoners cannot be relied upon to provide accurate information under circumstances in which reporting is based on subjective responses. Because much of the subjective information cannot be verified clinically, it is suggested that prisoners should be used only in studies with minimal risk and requiring minimal active cooperation. References and tables are included in the article.