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U.S. production and use of polychlorinated biphenyls (PCBs) ended in 1977 (Smith and Brown 1987). Concern continues about the persistence of PCBs in the environment and potential human health risks. Several strains of rats exposed to PCBs had preneoplastic changes of the biliary tract, intestine, and stomach (Morgan et al. 1981; National Cancer Institute 1978) and increased incidence of liver tumors (Carpenter 2000; Kimbrough et al. 1975). Liver toxicity and hepatocellular neoplasm incidence differed between PCB mixtures, were more severe in females than in males, and increased with dose in females (Mayes et al. 1998). The International Agency for Research on Cancer (IARC 1987) concluded that there is sufficient evidence of carcinogenicity of PCBs in animals but limited evidence in humans. Studies of PCB-exposed workers have generally found excesses for several cancer sites, but many were limited by sample size, imprecision in measuring PCB exposure, and/or inability to control for other risk factors and confounders (Carpenter 2000; Faroon et al. 2001). The mortality of 2,588 workers considered highly exposed to PCBs at two electrical capacitor plants in New York (plant 1) and Massachusetts (plant 2) was initially studied through 1975 (Brown and Jones 1981) and later updated through 1982 (Brown 1987) and 1998 (Prince et al. 2006). In the current study we expanded this cohort to include all employees who worked ≥ 90 days, and we ascertained their vital status through 1998. We used a semiquantitative job-exposure matrix (JEM) to estimate cumulative PCB exposure. Our goal was to investigate previously reported mortality excesses for cancers of the biliary passages, liver, and gallbladder (henceforth, liver cancer) and rectum (Brown 1987). Other a priori outcomes of interest included all-cancer mortality (Bertazzi et al. 1987), non-Hodgkin lymphoma (NHL) (Rothman et al. 1997; Hardell et al. 2001), breast cancer (Falck et al. 1992), melanoma and brain cancer (Loomis et al. 1997; Sinks et al. 1992), prostate cancer (Charles et al. 2003; Ritchie et al. 2003) and stomach and intestinal cancer (Mallin et al. 2004).