 Patients with COPD will be randomised to tiotropium or placebo in addition to their usual medication. They will be followed prospectively over 1 year and provide sputum for quantification of IL-6 and IL-8 at baseline and at 3 monthly intervals.Serum IL-6 will also be quantified at baseline and over the year. Changes in inflammatory markers will be assessed by analysis of area under the curve of log transformed data. Exacerbation frequency will be calculated from patient diary cards using a previously validated symptom-based exacerbation definition. 