One hundred and twenty-one regular soldiers between the ages of 18 and 34 years, who had lived and worked under identical conditions for the two previous years were examined. All subjects with respiratory symptoms of wheeze, dyspnoea, persistent cough or sputum were excluded. Smoking, per se, was not a reason for exclusion. Eighty-three "respiratorily fit" men, comprising 47 Maoris and 36 Europeans, were studied to see whether height, weight or obesity could account for the ethnic differences in lung function. The forced vital capacity in the Maoris was found to be about 9% lower than in the Europeans. The one-second forced expiratory volume of the Maoris was about 8% lower than in the Europeans. No significant difference could be found in the peak expiratory flow rates between the two ethnic groups. The only significant physical difference found between the two ethnic groups was that the Maoris were heavier for their height than the Europeans. Statistical tests showed that neither weight nor an obesity index accounted for the ethnic differences in lung function. Full laboratory investigation of these ethnic differences is recommended.