Seventy-one subjects who had previously been treated for tuberculosis up to 16 years before underwent pulmonary function assessment. Evidence of airways obstruction was found in 48 (68%). There was an inverse relationship between the extent of the disease on the original chest radiograph and the forced expired volume in one second (FEV1). A similar inverse relationship between the amount of sputum produced and the FEV1 and the original chest radiograph was also found. Treated pulmonary tuberculosis is a cause of significant chronic obstructive airways disease.