A follow-up study was conducted on 27 workers with a median of 25 years exposure to airborne cadmium. Two exposure groups had been selected a low exposure group of office, laboratory and supervisory personnel (n = 11, average urinary cadmium 13.1 micrograms/l); and a high exposure group of production workers with long histories of work in areas with substantial airborne cadmium (n = 16, average urinary cadmium 45.7 micrograms/l). An estimate of each subject's time-weighted-average inhalation exposure to cadmium was calculated from personal sampling data (1973-1976) and area sampling data (1943-1976). Based on the findings of another study, the average inhalation exposures in each of the work areas were adjusted for use of personal protective masks (respirators). Comparison of kidney function status between the high and low exposure groups showed a significant reduction in creatinine clearance, and increased uric acid and beta microglobulin excretion by the high group. Significant renal effects were associated with estimated average inhalation exposures of 63 micrograms/m3 over a 25 year period. The relationship between urinary cadmium excretion and cumulative exposure changed for higher exposures; this was consistent with the "critical concentration" model of cadmium's effects on the kidney.