Meta-analyses have shown an excess of vascular deaths in women with breast cancer given radiotherapy (RT). In women with breast cancer, RT to the supraclavicular lymph nodes gives a substantial radiation dose to the proximal carotid artery. RT is known to increase the risk of carotid stenosis and ischaemic stroke in head and neck cancer. A study base of 25,171 women with breast cancer was defined. A linkage between the study base and the Hospital Discharge Register yielded 1766 women who were diagnosed with a stroke after a breast cancer. The observed number of strokes was compared with the expected number in the background population. The Relative Risk (RR) of stroke in the study group with breast cancer was 1.12 (95% Confidence Interval (CI)=1.07-1.17). The increased risk was confined to the subtype cerebral infarction, RR=1.12 (95% CI=1.05-1.19). A statistically significant increase in the risk of stroke was seen among women with a history of breast cancer. Whether this risk is associated with the breast cancer disease per se or related to any treatment requires further study.