Axillary ultrasound (US) with fine needle aspiration biopsy (FNAB) of suspicious lymph nodes helps identify patients with axillary metastases preoperatively avoiding a 2-step axillary procedure. However, it does not accurately differentiate between low and high axillary tumour burden. Our aim was to determine the rationale of preoperative axillary US in screen-detected breast cancer. We retrospectively analysed patients, aged between 50 and 69 years, which had an invasive breast cancer diagnosed in the Slovenian National Breast Cancer Screening program between January 2012 and June 2017. Proportion of patients that proceeded directly to ALND and the proportion of patients with unnecessary ALND as a result of positive US-FNAB were calculated. Altogether 892 patients were eligible for analysis. Preoperative US of the axilla was performed in 856/892 (96%) patients, while 36/892 patients (4%) did not undergo US of the axilla. We have found out that upfront ALND due to positive US-FNAB was performed in 91/856 (10.6%) patients. 116/856 patients (13.6%) had tumours in inner quadrants and maximal mammographic tumour size ≤ 2 cm. Among them only 1/116 (0.9%) proceeded directly to ALND due to positive US-FNAB.The final pathology of those who underwent upfront ALND due to positive US-FNAB showed low axillary tumour burden not meeting the indications for ALND in 13/91 (14.3%) patients.Among patients without preoperative axillary US, only 1/36 (2.8%) met the indications for ALND. Our results showed that performing US of the axilla is not justified in screen detected breast cancer patients.