The results of body plethysmography in 607 coalminers from Lorraine, France, are analysed. The relationship between radiological aspects and tobacco consumption are discussed. When progressive massive fibrosis (PMF) is absent, total lung capacity (TLC) and slow vital capacity (VC) are related with profusion, but remain independant of X-ray type and tobacco consumption. Tobacco alters flows and FEV1/VC results. A 20% incidence of residual volume (RV) inflation is observed unrelated to X-ray aspect. When PMF is present, TLC results are more contrasted (8.9% restrictive defects, 5.7% hyperinflation) and obstructive pattern follows X-ray progression. Tobacco consumption induces more RV and functional residual capacity inflation. These results strongly support the fact that the effects of dust exposure vary with smoking. Consequently, the interactions between pneumoconiotic fibrosis and distension appear to be reflected by plethysmography. This method is useful for determining each functional pattern. It may also be of pronostic value but this needs to be confirmed by further studies.