The cancer incidence of 3,545 workers in the Finnish pulp and paper industry was assessed in a retrospective cohort study. The cohort included workers with continuous employment of at least one year between 1 January 1945 and 31 December 1961 and was followed until 31 December 1980. Six subcohorts were formed (sulfite mill, sulfate mill, paper mill, board mill, maintenance department, and power plant). Separate analyses were made for the 2,597 workers hired after 1 January 1945. The smoking habits were surveyed. Among the men, 196 cases of primary cancer were detected versus 203.8 expected [standardized incidence ratio (SIR) 96, 95% confidence interval (95% CI) 82-114], and there were 47 cancer cases among the women versus 57.9 expected (SIR 91, 95% CI 60-108). Lung cancer occurred in 78 men (62.6 expected, SIR 125, 95% CI 98-155), and the excess was the most prominent for the male board mill workers (40 observed, 81.1 expected, SIR 222, 95% CI 158-302), particularly after 20 year's latency (25 observed, 7.8 expected, SIR 323, 95% CI 209-476). Analogous excesses of lung cancer occurred among the men (especially the male board mill workers) who began work after 1 January 1945. The findings were not explained by smoking habits.