Treatment of chronic obstructive pulmonary disease (COPD) with inhaled and oral corticosteroids is common, although their exact role is unclear. Previous studies suggest these drugs may reduce decline in lung function in this group of patients. We report a study investigating the effect of inhaled beclomethasone diproprionate (BDP) on lung function and symptoms in a group of patients with COPD. Treatment was given for 2 years, and the decline in FEV1 in individual patients calculated over this period. Ninety-eight patients were randomized for the study, 59 completing 2 years of treatment. Patients withdrawn had more severe airflow obstruction. Decline in FEV1, measured both prior to and after bronchodilator, was less in patients receiving inhaled BDP, although the differences failed to reach statistical significance except in a subgroup of patients with more severe airflow obstruction. Exacerbation rates were also reduced by inhaled BDP, but again the differences failed to reach conventional levels of statistical significance. The results of this study are consistent with previous published work, but further insight into the long-term role of corticosteroids in COPD await the publication of large studies which have recently been completed. Although the changes seen in this study and others are numerically small, the rate of decline in FEV1 returned to normal levels expected from age-related decline, and hence such treatment combined with other strategies may well have a significant role in the long-term treatment of this condition.