Analysis of the lifetime occupation histories of 1030 patients with bladder tumours compared to control groups showed two patterns of industrial hazard. The classic pattern showed risk from all periods of exposure and the development of tumours at a lower age. Chemical dyeworkers, and possibly textile dyers and cutters and hairdressers, showed this pattern. A long-term pattern, present among weavers, tailors, tailor's pressers and possibly among cooks, electricians and some engineering workers showed risk after long periods of exposure only. The reality of the risks was supported by the larger proportion of bladder patients (53 per cent compared to 35 per cent) who had only one occupation and by comparison with census data.