Background: The presence of airways obstruction is currently defined by GOLD guidelines on the basis of the post-bronchodilator FEV1/FVC. It has been proposed that the traditional FVC can be replaced with the shorter and less demanding FEV6 for detecting airway obstruction. Methods: A population-based sample of 1349 adults participated in the Burden of Obstructive Lung Disease (BOLD) study in Austria. Specially trained and certified technicians conducted pre-BD and post-BD spirometry according to American Thoracic Society guidelines and administered standardized questionnaires. Ninety three percent of the post-BD test sessions were acceptable, and included in this analysis. The NHANES III reference equations were used to calculate predicted values and lower limits of normal (LLN) for FEV1, FEV6, FVC, FEV1/FVC and FEV1/FEV6. Results: The post-BD FEV1/FVC was below the LLN in 199 (15.8%) subjects. The sensitivity of the FEV1/FEV6 for airway obstruction depended greatly on the threshold of percent predicted FEV1 also used in the definition. The overall sensitivity of FEV1/FEV6 for a diagnosis of airway obstruction as defined by FEV1/FVC (including participants with an FEV1 above the LLN) was 72.9%, with 98.8% specificity. The sensitivity increased to 98.0% when a low FEV1 was also required to diagnose post-BD airway obstruction. The discordant cases had long forced expiratory times; often showed a flow-volume curve pattern consistent with twocompartment emptying; and were more often never-smokers. Conclusion: Six second spirometry maneuvers (which measure FEV6) are as sensitive and specific for post-BD airway obstruction as traditional (prolonged exhalation time) FVC maneuvers only when the definition of airway obstruction includes a low FEV1.