A stereotactic head frame has been developed which is accurately relocatable over an extended period of time, is non-invasive, and yet is rigidly fixed relative to the patient's skull. Eight patients with malignant brain tumours were studied by positron emission tomography scanning using ISFUDR and computed tomography scan. Serial biopsies were performed and were studied by routine histological methods and using the monoclonal antibody Ki 67. © 1990 S. Karger AG, Basel.