The use of Breast Conserving Surgery (BCS) followed by radiotherapy (BSC-RT) in pT1 (2cm) and pT2-tumours (2-5cm) was investigated in the Netherlands from 1990 to 2001. From the Netherlands Cancer Registry, patients were selected with invasive tumours <5.0cm. Trends were determined and explanatory factors were determined by multivariate logistic regression. Over the period 52,937 pT1-tumours and 36,285 pT2-tumours were diagnosed. The percentage BCS and BCS-RT in patients 80 years or older remained lowest. Multivariate logistic regression revealed that older age (70+), tumour size >2cm, positive clinical nodes and medium hospital size decreased the chance of BCS. For BCS-RT the same factors and negative pathological nodes decreased the chance of BCS-RT. Between regions large differences were seen. Cancer registry data are useful to monitor the guideline implementation strategies. Multidisciplinary treatment planning, surgeon and patient education could increase the use of BCS combined with RT in all age groups.