Detection of HER-2/neu alterations is increasingly used in breast cancer patients for therapeutic purposes. This study examines the reliability of HER-2/neu immunocytochemical assessment on 66 cytospin smears obtained by fine-needle aspiration biopsy from breast cancer patients. Results were compared with those obtained by both fluorescence in situ hybridization (FISH) on fine-needle aspirate (FNA) and immunohistochemistry (IHC) on matched histologic section. Concordance between immunocytochemistry (ICC) and FISH was 78% and between ICC and IHC was 84%. Discordance mainly concerned seven unamplified cases that resulted positive by ICC and four cases scored negative by IHC but positive by ICC. Simultaneous assessment of HER-2/neu by ICC, IHC, and FISH was available in 24 cases; the concordance was 75%. In this study, the false positivity of immunocytochemical technique represents the major criticism. In our experience, FISH remains the most objective and powerful technique for HER-2/neu assessment on breast cancer FNAs. Diagn. Cytopathol. 2003;28:142–146. © 2003 Wiley-Liss, Inc.