BACKGROUND Sensitivity to beryllium was investigated among workers at an aluminum smelter in Norway as a consequence of the findings in an occupational exposure survey. METHODS Three hundred and sixty-two employees and 31 reference persons were tested for sensitization to beryllium with the beryllium lymphocyte proliferation test (BeLPT) based on specifications by the US Department of Energy in 2001. The results are reported as abnormal, borderline, or normal. RESULTS One person (0.28%) from the aluminum smelter was found to have abnormal results in two separate blood samples and is sensitized to beryllium. Three other persons had one abnormal test that was not confirmed by a second test. One person in the reference group had one abnormal and one normal test result. No borderline samples were detected. None of the employees with one or more abnormal sample results had pot room asthma. The sensitized individual worked in a Soederberg line in 1972-1974. The beryllium concentration in the work atmosphere is estimated to have been similar as today (0.1-0.3 microg/m(3)), but work routines, etc. would cause higher total exposures. CONCLUSIONS Only one sensitized person of 362 is in line with what is found in other studies in the aluminum industry. The low number, compared with the beryllium handling industry, may be attributable to lower work atmosphere concentrations, beryllium speciation effects, or use of respiratory protection equipment. Pot room asthma does not appear to be associated with beryllium sensitization.