BACKGROUND: Little research has investigated cancer care in UK prisons. We wished to identify the number of new cases and the most common cancer diagnoses occurring each year in London prisoners, and the place of death for those who died from their disease. METHODS: Using the database of the Thames Cancer Registry, we identified cancer diagnoses in residents of seven London prisons from 1986 to 2005 and the place of death of patients dying from their disease between 1996 and 2005. RESULTS: On average, 31 patients were recorded as diagnosed with cancer while in prison within each 5-year period. In women, 83% (85/102) of diagnoses were in situ carcinoma of the cervix, and in men, 19% (11/57) were of lung cancer. None of the 25 patients recorded as dying from their disease died in prison. Most died in hospitals (48%, 12/25) or in hospices (28%, 7/25). CONCLUSIONS: London prisons contribute a small number of patients each year who require NHS cancer care, including those with advanced cancer who are released before death. Future studies should investigate cancer incidence for the national prison population, methods for improving screening coverage and follow-up, the timeliness of access to cancer treatments and end-of-life care, and prisoners' and health professionals' experiences of care.