The authors conducted a proportional mortality study of 1,043 deaths that occurred between 1956 and 1992 among men who used mainly dichloro-diphenyl-trichloroethane (DDT) in an anti-malarial campaign in Sardinia, Italy, during the late 1940s. For each cause of interest, investigators compared observed deaths with expected deaths. The estimated DDT exposure ranged from 170 to 600 mg/m3 in indoor operations and from 24 to 86 mg/m3 in outdoor operations. Workers directly exposed to DDT had a significant increase in risk for liver and biliary tract cancers (PMR = 228; 95% confidence interval = 143, 345) and multiple myeloma (PMR = 341; 95% confidence interval = 110, 795). However, the PMR for liver and biliary tract cancers was also elevated among workers who did not have direct occupational contact with DDT, and the authors observed no increase in either PMR, by number of days in exposed jobs. Perhaps DDT did not increase the risk or perhaps occupational exposure, although quite high, did not further increase the risk, compared with the heavy baseline exposure of the entire Sardinian population, (i.e., mainly through diet and drinking water). Expansion of the cohort to include all exposed workers, and collection of information to improve exposure assessment are needed to clarify these findings.