Measurements have been made of forced expiratory volume (f.e.v.) and forced vital capacity (f.v.c.) in two groups of rural Israeli Jews aged 20 to 30, born in the Yemen and in Kurdistan. The Jews from Kurdistan had a significantly higher f.e.v. and f.v.c. than the Jews from the Yemen, but there was no difference in the f.e.v. % ratio. These differences were not accounted for by differences between the groups in age, nor entirely by morphological differences. The pattern of correlations with anthropometric variables suggested that in the Jews from the Yemen the lung function values were related to linearity rather than to body bulk, while in the Jews from Kurdistan they were better correlated with overall size and mass of the body. f.e.v. and f.v.c. were elevated in smokers compared to non-smokers, possibly owing to an increased respiratory effort to cope with a reduction in the f.e.v. % ratio.