A cohort of males who started work between 1946 and 1965 inclusive in nine English steel foundries and who worked in these foundries at least one year has been followed prospectively until 1978. Mortality from lung cancer was significantly raised among workers employed in the foundry and fettling shop areas (standardized mortality ratios 142 and 173, respectively). Most occupational categories in these two areas had more lung cancer deaths than expected, but the standardized mortality ratios were the largest for the furnace bricklayers, fettlers, and heat treatment furnacemen. There was some evidence of risk increasing with length of employment. There were marked differences in the standardized mortality ratio for lung cancer between study foundries. By year of entry the lung cancer risk was fairly constant, in contrast to the improvement in mortality from diseases of the respiratory system over the same period.