A case control study of lung cancer in truck drivers was conducted. The cohort consisted of 996 cases of lung cancer occurring in members of the Teamsters Union who had filed claims for pension benefits and who died in 1982 and 1983. The comparisons consisted of 1085 union members who died from causes other than lung cancer, bladder cancer, and motor vehicle accidents during the same period. The next of kin were interviewed to obtain information on work history and potential confounders such as smoking, dietary habits, and asbestos (1332214) exposure. Odds ratios (ORs) for lung cancer were computed for type of job in the trucking industry, miles driven, whether the truck had a diesel engine, and similar factors. For subjects employed after 1959, the approximate time that diesel engines were introduced into the trucking industry, the risk of lung cancer increased with increasing duration of employment for short and long haul drivers. When no cutoff date was used the risk of lung cancer was not related to length of employment. When 1964 was used as the cutoff date, the lung cancer risk for long haul truck drivers with 13 plus years driving experience was significantly increased, OR 1.64. The risk was elevated for drivers who drove primarily diesel powered trucks. Truck mechanics revealed no increased risk for lung cancer that varied with duration of employment. There were no significant interactions between Lung cancer risk, exposure, smoking, or asbestos exposure. The authors conclude that positive trends in lung cancer risk have been established for persons employed as long haul truck drivers after 1959 and 1964 and for truck drivers who drove mostly diesel trucks. The study is limited, however, because of the lack of data on exposure to diesel fumes, possible job misclassification, and lack of sufficient latency to observe a lung cancer excess.