We evaluated the effectiveness and the cost of axillary staging in breast cancer patients by ultrasound-guided fine-needle aspiration cytology (US-FNAC), sentinel node biopsy (SNB), and frozen sections of the sentinel node to achieve the target of the highest number of immediate axillary dissections. From January 2003 through October 2005, a total of 404 consecutive eligible breast cancer patients underwent US-FNAC of suspicious axillary lymph nodes. If tumor cells were found, immediate axillary dissection was proposed (33% of node-positive cases). If US or cytology was negative, SNB was performed. Frozen sections of the sentinel node allowed immediate axillary dissection in 31% of node-positive cases. The remaining 36% underwent delayed axillary dissection. We compared our policy with clinical evaluation of the axilla, showing better specificity of US-FNAC, the cost balanced by a 12% reduction of SNBs, and a marked reduction of unnecessary axillary dissections resulting from false-positive clinical staging. Moreover, the comparison between our policy and permanent histology of the sentinel node showed an 8% cost saving, mainly associated with the immediate axillary dissections. US-FNAC of axillary lymph nodes in breast cancer patients reliably predicts the presence of metastases and therefore refers a significant number of patients to the appropriate surgical treatment, avoiding an SNB. As cost saving to the health care system in our study is mainly related to one-step axillary surgery, US-FNAC of axillary lymph nodes and frozen section of the sentinel node generate significant cost saving for patients who have metastatic nodes.