Abstract: A diagnostic whole body counter includes both a detector for external or beta radiation and a detector for internal or gamma radiation. A subject stands on a platform and external radiation detectors inset in a back wall of the radiation detector are employed to quickly check for any external radiation on the subject. After it is determined that no external radiation is present, the subject is scanned using an internal radiation detector which is transported vertically along the length of the subject. An intrinsic germanium detector is employed as the internal radiation detector to provide a highly accurate determination of radiation dosage. Variable diameter lead collimators are positioned in front of the internal radiation detector to vary the size of the area scanned by the internal radiation detector.