We have measured serum aluminium and urinary aluminium/creatinine ratios in 235 aluminium workers and 44 controls to examine the association between occupational exposure to airborne aluminium and aluminium absorption. Serum and urine samples were taken before and after a 3- to 5-day work shift. Occupational exposure was estimated from aluminium measurements of respirable and total particulates in air. Median exposure values were 25 and 100 micrograms m-3, respectively. Serum aluminium and urinary aluminium/creatinine ratios did not change significantly during the shift; however, both pre-shift and post-shift serum aluminium and urinary aluminium/creatinine ratios were increased in the exposed group. Occupational exposure was associated with serum aluminium increments of 1.32 micrograms l.-1 (P = 0.01) pre-shift, and 0.96 micrograms l.-1) (P = 0.08) post-shift. Greater and more significant differences were seen between exposed and controls for the urinary aluminium/creatinine ratios [5.67 micrograms g-1 (P < 0.01) pre-shift; 8.01 micrograms g-1 (P < 0.01) post-shift]. Urinary aluminium/creatinine ratios were greater in plants with higher aluminium exposures. These results are consistent with the systemic absorption of aluminium from occupational exposure and suggest the presence of a sensitive uptake process for airway aluminium.