Nasal histology and nickel concentration in the plasma and urine of nickel workers were reexamined after 4 a for an evaluation of the effect of improvements in the refining process and work conditions. Ninety-eight (31%) nickel workers who were part of a previous study were reexamined. In addition, 33 of the original 38 workers with nasal epithelial dysplasia were studied for possible regression of the histological changes. Reduction in the atmospheric content of nickel and improved hygienic conditions lowered the concentration of nickel in plasma and urine by approximately 50%. The mean histological score and frequency of dysplasia was virtually the same in the two investigations, 12 and 13%, respectively. Nasal biopsies are of limited diagnostic value in the examination of individual cases. However, the method seems to be of value in identifying and monitoring groups of persons with increased risk of developing nasal carcinoma.