lung cancer with increasing years of exposure. The investigators studied lung cancer deaths in Teamsters Union truck drivers and support personnel, using death certificates from pension files to identify 1,058 cases and 1,160 controls. Information on work history and potential confounders were collected from next-of-kin interviews. Using duration of employment as a categorical variable and considering employment after 1959 (when presumed dieselization occurred for most trucking companies), the risk of lung cancer increased with increasing years of exposure, for both long-haul and short-haul drivers. Using 1964 as the cutoff, a similar trend was observed for long-haul drivers. Using 1964 as the cutoff (presumed dieselization for independent driver and non-trucking firms), long-haul drivers continued to show a significant positive trend, while short-haul drivers did not show a positive trend. For truck drivers who primarily drove diesel trucks and worked for 35 years, the OR was 1.89 (95% CI = 0.81, 2.22). The main strengths of the study are availability of detailed records from the Teamsters Union, a relatively large sample size, availability of smoking data, and measurements of exposure. The limitations of this study include possible misclassifications of exposure and smoking, lack of levels of diesel exposure, a smaller nonexposed group, and an insufficient latency period. Substantive evidence from cohort studies linking diesel exhaust exposure to lung cancer comes from the Garshick et al. (1988) study of 55,407 railroad workers, conducted in the United States. Relative risks (RRs) of 1.57 (95% CI = 1.19, 2.06) and 1.34 (95% CI = 1.02,