To apply the probabilistic approach to a series offine needle aspiration (FNA) samples of male breast lesions and determine the accuracy and reproducibility of this method of reporting in men. All male breast surgical specimens with a preoperative breast FNA at our institution from 1994 to 2005 were identified. The FNAs were blindly reviewed by 2 groups of observers and classified in 1 of 5 categories using published reporting guidelines: positive, suspicious, atypical, proliferative without atypia and unremarkable. The histologic and cytologic diagnoses were correlated. The interobserver variation was determined. A total of 138 FNAs were performed for 123 male patients. Histologic correlation was available for 23 satisfactory FNAs. A total of 11 of 11 carcinomas (100%) were classified as positive, suspicious or atypical. Of 12 benign masses, 11 (91.6%) were classified as proliferative without atypia or unremarkable. One case of gynecomastia was classified as atypical by 1 observer but deemed not atypical with consensus review. The kappa statistic for benign and atypical/suspicious/malignant categories was 0.90. Based on this series, the probabilistic approach can be applied to the reporting of FNAs of male breast lesions. Gynecomastia may result in an atypical cytologic diagnosis.