Cadmium is commercially important and is present in cigarettes, but the chronic respiratory effects of inhaling cadmium remain controversial. We report the effects of cadmium fume inhalation in the largest and most complete occupationally exposed population studied to date. We studied (i) 101 of 102 men who were alive and had worked in a copper-cadmium alloy plant for one year or more since it opened in 1926, (ii) 96 unexposed controls matched for age, sex and occupational status from the same factory. Cumulative exposure to cadmium was estimated from company records and since 1951, from measured airborne levels. Smoking habits were similar in the two groups. Significant differences were found between the values for cadmium workers and expected values (the latter derived from regression equations for controls) for the measures FEVI, - 194 ml (p<0.05); FEV1/FVC%, - 6.5% (p<0.001); TLCO, - 0.82 mmol/min/kPa (p<0.001); Kco, - 0.25 mmol/min/kPa/l (p<0.001); Radiographic TLC + 461 ml (p<0.001); RV + 402 ml (p<0.01); RV/RTLC/o + 2.9% (p<0.02). Cadmium workers first employed before 1950 and with high cumulative exposures showed the greatest reduction in FEVI, FEVI/FVClo, TLCO, Kco. Eighteen per cent of cadmium workers had radiographic emphysema at independent assessment, compared with 7% of controls. These results are consistent with cadmium fume inhalation causing emphysema.