The Atlas of Cancer Mortality for England and Wales showed pronounced excesses of male mortality from nasal and bladder cancer in certain London boroughs. These excesses were investigated by case-referent studies using death certificate data for male deaths, 1968-78. Nasal cancer was found to be significantly associated with occupations involving heavy exposure to wood dust. Bladder cancer was significantly associated with occupations in road transport driving and in the handling of leather, whereas consistently raised relative risk ratios were also found for wood-workers, engineering fitters, printers, machinists, plumbers, and motor mechanics. These findings highlight the potential role of occupational factors in cancer causation in London.