In this, the fifth of a series of papers concerning the mortality of steelworkers, the variation in mortality of coke plant workers according to calendar period and length of employment at several work stations within the coke plant is examined. The findings of particular interest are: (1) The excess of respiratory cancer previously reported for coke plant workers is limited to men employed at the coke ovens, the relative mortality for this disease being 2.5 times that predicted. (2) The greatest part of this excess is accounted for by an almost five-fold risk of lung cancer in men working on the tops of the coke ovens. (3) A 10-fold risk of lung cancer is observed for men employed five or more years at full-time topside jobs. Fifteen lung cancer deaths were observed among the 132 men in this group compared to 1.5 deaths expected. (4) The apparent differential in respiratory cancer rates for white and nonwhite coke plant workers, reported in the fourth paper of this series, is accounted for by differing distributions by work area and the unusually high lung cancer risk for topside workers. Lung cancer mortality for white and nonwhite coke plant workers employed at work stations other than the top of the coke oven is comparable. (5) A deficit of deaths from heart disease, previously reported for similar occupational groups, is also seen for coke oven workers. (6) Coke plant workers employed only in the nonoven area may be at excess risk of digestive cancer.