OBJECTIVE: Intraoperative imprint cytology (IOIC) of sentinel lymph node (SLN) allows axillary surgery in one sitting in patients with positive SLN, but a second operation may then become necessary to clear margins of the primary tumor. Axillary ultrasound now identifies approximately half the node-positive axillae, reducing the need for intraoperative testing. We studied how many second operations were avoided by IOIC of the SLN. STUDY DESIGN: Large district general hospital breast unit, retrospective review. RESULTS: We reviewed 491 patients with negative preoperative axillary ultrasound who underwent SLN biopsy and IOIC over an 8-year period. A total of 108 patients (22%) had macrometastasis in the SLN, and 81 (75%) were diagnosed intraoperatively and underwent axillary clearance in the same sitting. However, 13 of those 81 patients required further surgery to get adequate margins for primary tumor. CONCLUSION: Only 22% of patients in this study had positive sentinel lymph nodes in the axilla. The false neg-ative rate of IOIC was 25%. 16% of patients whose node positivity was intraoperatively diagnosed still required further surgery for primary tumor. IOIC helped to avoid 81 cases of delayed axillary clearances and 68 reoperations in 491 patients. Imprint cytology is inexpensive and quick and remains a worthwhile addition to breast cancer surgery. © Science Printers and Publishers, Inc.