BACKGROUND: This population-based study describes the implementation of the sentinel node biopsy (SNB) in breast cancer patients in the Netherlands. We examined the extent of use over time of SNB in women who were considered eligible for SNB on the basis of their clinical status. METHODS: The study included a total of 35,465 breast cancer patients who were diagnosed with T1-2 tumours (5.0 cm), negative axillary lymph node status and no distant metastases upon clinical examination between 1st January 1998 and 31st December 2003 in six Comprehensive Cancer Centre regions in the Netherlands. Information on axillary surgery was classified as SNB alone, SNB+axillary lymph node dissection (ALND), ALND alone or none. Patterns of use of axillary surgery were summarised as the proportion of patients receiving each surgery type. RESULTS: Overall, 25.7% of patients underwent SNB alone, 19.1% underwent SNB+ALND, 50.0% had ALND alone and 5.2% did not have axillary surgery. SNB was more common in women who had breast-conserving surgery: 50.5% of patients who received breast-conserving surgery underwent SNB compared to 40.7% of patients who had mastectomy (p<0.0001). Amongst patients receiving breast-conserving treatment, 31.7% had SNB as final axillary surgery, whilst 20.5% of patients who had mastectomy had SNB alone (p<0.0001). The proportion of women who underwent a SNB alone or in combination with ALND increased over the period 1998-2003, from 2.1% to 45.8% and from 6.7% to 24.8%, respectively. There were marked differences in the patterns of dissemination of the use of SNB between regions: by 2003, the difference between the regions with the highest and lowest proportion of use was 25%. CONCLUSIONS: SNB has become the standard-of-care for the treatment of breast cancer patients clinically diagnosed with T1-2 tumours, clinically negative lymph nodes and without distant metastases. In 2003, 70.6% of patients with early breast cancer in the Netherlands received SNB, and within this group, 64.9% of patients had SNB as the final axillary treatment. Implementation of SNB may depend on factors associated with regional organisation of care.