Since there are no published data on breast cancer in British black women, we sought to determine whether, like African-American women, they present at a younger age with biologically distinct disease patterns. The method involved a retrospective review of breast cancer to compare age distributions and clinicopathological features between black women and white women in the UK, while controlling for socioeconomic status. All women presented with invasive breast cancer, between 1994 and 2005, to a single East London hospital. Black patients presented significantly younger (median age of 46 years), than white patients (median age of 67 years (P=0.001)). No significant differences between black and white population structures were identified. Black women had a higher frequency of grade 3 tumours, lymph node-positive disease, negative oestrogen receptor and progesterone receptor status and basal-like (triple negative status) tumours. There were no differences in stage at presentation; however, for tumours of < or =2 cm, black patients had poorer survival than white patients (HR=2.90, 95% CI 0.98-8.60, P=0.05). Black women presented, on average, 21 years younger than white women. Tumours in younger women were considerably more aggressive in the black population, more likely to be basal-like, and among women with smaller tumours, black women were more than twice as likely to die of their disease. There were no disparities in socioeconomic status or treatment received. Our findings could have major implications for the biology of breast cancer and the detection and treatment of the disease in black women.