Lung cancer risk in relation to airborne levels of hexavalent chromium was analyzed for chromium chemical production workers studied by Hayes, Lilienfeld, and Snell. Hayes et al [18] had observed statistically significant increases in lung cancer mortality among chromium chemical production workers hired during 1945-1959 and followed to mid-1977. A dose-response was observed by Hayes et al. in that long-term workers had a higher lung cancer risk than short-term workers. Concurrent exposure data for the study plant were abstracted from the records of a local health department. The usual air concentration of hexavalent chromium was estimated as 413 micrograms per cubic meter (micrograms/m3) during 1945-1949. Cumulative exposure estimates for individual workers could not be developed with available information. Instead, cumulative exposures in terms of micrograms/m3-years were estimated for groups of short-term workers and long-term workers (cumulative exposure = usual exposure level in micrograms/m3 X average length of exposure). For workers hired during 1945-1949, cumulative exposures were estimated as 670 and 3,647 micrograms/m3-years for short-term and long-term workers, respectively. Like most estimates based on historical data, these exposure estimates are subject to uncertainty. Nevertheless, these results suggest a potential excess risk of death from lung cancer among U.S. workers exposed to the current permissible exposure limit (PEL) for hexavalent chromium of 52 micrograms/m3 because such workers could accumulate exposures (micrograms/m3-years) similar to those associated with excess risk in Hayes et al's cohort. Moreover, many current workers are estimated to be exposed to levels above the PEL. Further exploration of the dose-response relationship for chromium carcinogenesis is indicated.