In 1985, Acquavella, et al.  reported the results of a cohort mortality study of white male workers ever employed at the Pantex Plant between 1951 and the end of study date, December 31, 1978. Compared to U.S. death rates, the mortality experience of these workers suggested a strong healthy worker effect overall, but non-significant elevations were observed for leukemia and brain cancer. For the current analyses, the National Institute for Occupational Safety and Health (NIOSH) expanded the study population to include workers of both genders and all races ever employed between 1951 and 1978 and extended vital status follow-up through 1995. Summary Standardized Mortality Ratios (SMRs) were generated for these workers (the full NIOSH cohort). Workers terminating or deceased by December 31, 1978, for whom complete employment records were available (the early-term subcohort), were included in SMR and Standardized Rate Ratio (SRR) duration of employment analyses. The all-cause SMR for the early-term subcohort (0.98, 95% confidence interval (CI) = 0.92-1.05) was higher than that seen in the full NIOSH cohort (SMR=0.81, 95% CI=0.76-0.86) and by Acquavella et al.  (SMR=0.72, 95% CI=0.64-0.81) and was close to that expected from U.S. population rates. Brain cancer was no longer elevated in the full NIOSH cohort (SMR=0.51, 95% CI=0.17-1.19) in the updated analysis, although the confidence intervals span unity. The leukemia SMR was elevated (earlyterm subcohort SMR=1.47, 95% CI = 0.73-2.63) but SRRs showed no evidence of a positive exposure-response relation with increasing duration of employment. Lung cancer SMRs with 10and 15-year lags were just below expectation. Breast cancer was elevated only in workers with employment durations of 5 to 10 years. The SMR for prostate cancer was as expected, but this outcome showed a statistically significant positive exposure-response !slope: 1.36X10(-5) per person-year (PY)Xyear of employment (YOE), standard error: 4.31X10(-6) per PY X YOE], with a very high, though imprecise, point estimate (SRR=7.57, 95% CI=1.03-55.72) for workers employed at least 20 years with a 10-year lag imposed. Multiple myeloma also exhibited a statistically significant positive exposure-response. Due to the potential for positive bias in the early-term subcohort, caution should be exercised in generalizing the exposure-response results. These findings suggest the need for collection of full employment information about workers employed beyond 1978, as well as the estimation of occupational exposure for Pantex workers.