['Sentinel lymph node (SLN) biopsy has proved to be an accurate method for detecting nodal micrometastases in previously untreated patients with early-stage breast cancer. We investigated the accuracy of this technique for patients with more advanced breast cancer after neoadjuvant chemotherapy.', 'Patients with stage II or III breast cancer who had undergone doxorubicin-based neoadjuvant chemotherapy before breast surgery were eligible. Intraoperative lymphatic mapping was performed with peritumoral injections of blue dye alone or in combination with technetium-labeled sulfur colloid. All patients were offered axillary lymph node dissection. Negative sentinel and axillary nodes were subjected to additional processing with serial step sectioning and immunohistochemical staining with an anticytokeratin antibody to detect micrometastases.', 'Fifty-one patients underwent SLN biopsy after neoadjuvant chemotherapy from 1994 to 1999. The SLN identification rate improved from 64.7% to 94.1%. Twenty-two (51.2%) of the 43 successfully mapped patients had positive SLNs, and in 10 of those 22 patients (45.5%), the SLN was the only positive node. Three patients had false-negative SLN biopsy; that is, the sentinel node was negative, but at least one nonsentinel node contained metastases. Additional processing revealed occult micrometastases in four patients (three in sentinel nodes and one in a nonsentinel node).'] Is sentinel lymph node biopsy accurate after neoadjuvant chemotherapy for breast cancer?