A standard outcome parameter for pharmacological trials in COPD has not yet been defined. Therefore, it is the aim of this review to evaluate frequently used parameters for their eligibility as assessment and outcome parameters in COPD.A review of the actual scientific literature was performed.It is recommended to continue to rely primarily on the FEV (1), which has been used as a primary variable in the vast majority of trials. In addition, further parameters, such as FVC and IC/TLC should be determined. If available, additional information is provided by RV/TLC, K (co), PaO (2) and PaCO (2). FEV (1) is not a surrogate parameter for dyspnoea, quality of life, and exercise tolerance, which should therefore be assessed separately. Frequency and severity of exacerbations and mortality are important outcome parameters in long-term trials. Complex indices, such as the BODE index, may be superior to single variables.No single additional parameter has been evaluated sufficiently in order to substitute FEV (1) as the standard parameter for the assessment and outcome in COPD.