Background: Styrene, an organic solvent whose worldwidc use is increasing, has been classified by the International Agency for Research on Cancer in Group 2B, possibly carcinogenic to humans. Mortality was updated through 1998 for a cohort of 5,205 Washington State workers exposed to styrene between 1959 and 1978 at two reinforced plastic boat building plants. The a priori hypothesis was that excesses in leukemia and lymphoma would be found. .Methods: Standardized mortality ratios (SMR) and 95% confidence intervals (CI) used U.S. and Washington State rates. Results: Overall, 860 deaths were observed (SMR=0.97, CI 0.91-1.04). Statistically significant excess mortality was observed for esophageal cancer (n=12, SMR=2.19, CI 1.13-3.82), prostate cancer (n=24, SMR=1.77, CI 1.13-2.63) and accidents (n=99, SMR=1.28, CI 1.041.56). Among 2,062 highly exposed workers who ever worked in high exposure departments, urinary tract cancer (n=6, SMR=3.10, CI 1.136.75) and pneumoconioses and other respiratory diseases (n=12, SMR=2.56, CI 1.32-4.47) were significantly elevated. All 12 deaths were from "other respiratory diseases", not pneumoconioses. Urinary tract and prostate cancer had statistically significant trends toward increasing SMR with increasing duration of employment in high-exposure departments; the exposure-response relationship for "other respiratory diseases" showed no dear trend. Among 3,143 workers in the low exposure subcohort, esophageal and prostate cancer and Cirrhosis of the liver mortality were significantly elevated. No excess for leukemia or lymphoma was found. With Washington State rates the total cohort had excesses for all deaths; all cancers; cancer of the esophagus, prostate, and other and unspecified sites; cirrhosis; and accidents. Conclusion: Findings are comparable with those of other cohort studies of styrene-exposed workers. Although we found no evidence for an excess in mortality from leukemia and lymphoma, statistical power is limited, especially for the high-exposure subcohort. Kidney cancer and respiratory disease mortality may be associated with exposure to higher levels of styrene.