Three-hundred and seventy intraoperative cytologies are presented and compared with synchronously performed frozen sections. Cytologic smears and frozen sections were misinterpreted in 1.6% and 0.8% of cases, respectively; the rate of diagnostic errors between the two techniques is comparable given the lack of experience with intraoperative cytology at the beginning of the study. Intraoperative cytology is a suitable technique for a variety of lesions, but it is most helpful in the field of neuro-oncological pathology, certain infectious diseases, lesions of the hematopoietic system, and most epithelial tumors. Cytologic smears afford better morphologic preservation and detail than frozen sections. Techniques are outlined and discussed. Diagnostic criteria of selected cases are presented, and pitfalls are analyzed.