The smear preparation technique is usually employed intraoperatively for stereotaxic brain tumor biopsies, whereas the frozen section technique is used in conventional operations, where larger tissue specimens can be obtained. 130 brain tumor biopsies were processed with the frozen section technique and postoperatively submitted to immunohistochemical examination. Subsequent paraffin embedding was not performed. In our study, frozen section diagnosis corresponded in 84% with the immunohistochemistry. Broggi et al. (1984) and Kleihues et al. (1984) demonstrated a similar positive correlation between intraoperative smear preparations and postoperative paraffin embedding. In our investigation, the greatest difficulties arose in cases of suspected lymphoma. Postoperatively, all lymphomas could be immunohistochemically clarified. Due to insufficient material 8% of the cases remained unclarified. Compared to smear preparation, the intraoperative frozen section technique during intervention provided a more accurate assessment of the histology. Furthermore the time needed for the procedure is not much longer than for smear preparation techniques. Reliable antibodies can be used in the remaining frozen material for further differentiation.