OBJECTIVE: To use newly available self-assigned ethnicity information to investigate variation in breast cancer screening uptake for women from the 16 specific ethnic groups within the broad Asian, Black and White groups that previous studies report. SETTING: National cancer screening programme services within London. PARTICIPANTS: 655,516 female residents aged 50-69, invited for screening between March 2006 and December 2009. Ethnicity information was available for 475,478 (72.5%). White British women were the largest group (306,689, 46.8%), followed by Indian (34,687, 5.3%), White Other (30,053, 4.6%), Black Caribbean (25,607, 3.9%), White Irish (17,271, 2.6%), Black African (17,071, 2.6%) and Asian Other (10,579, 1.6%). OUTCOME MEASURES: Uptake for women in different ethnic groups aged 50-52 for a first call invitation to the programme, and for women aged 50-69 for a routine recall invitation after a previous mammography. Uptake is reported (1) for London overall, adjusted using logistic regression, for age at invitation, socioeconomic deprivation and geographical screening area, and (2) for individual areas, adjusted for age and deprivation. RESULTS: White British women attended their first call (67%) and routine recall (78%) invitations most often. Indian women were more likely to attend their first (61%) or routine recall (74%) than Bangladeshi women (43% and 61%, respectively), and Black Caribbean women were more likely than Black African women to attend first call (63% vs 49%, respectively) and routine recall (74% vs 64%, respectively). There was less variation between ethnic groups in some screening areas. CONCLUSIONS: Breast cancer screening uptake in London varies by specific ethnic group for first and subsequent invitations, with White British women being more likely to attend. The variation in the uptake for women from the same ethnic groups in different geographical areas suggests that collaboration about the successful engagement of services with different communities could improve uptake for all women.