Background:The 6-min walk test (6MWT) is widely used to assess patients with chronic lung disease (CLD). Anecdotal reports and studies in small numbers of patients with CLD suggest that complications associated with the 6MWT are rare. This study reports the incidence of observed adverse events during the 6MWT in patients referred to an outpatient pulmonary rehabilitation service.Methods:Seven hundred and forty-one patients with stable CLD (chronic obstructive pulmonary disease (COPD), n = 572) completed the 6MWT in accordance with a standardized protocol that included continuous monitoring of oxygen saturation (SpO(2)) and heart rate (Polar).Results:Adverse events occurred in 43 tests (6%). One 6MWT was terminated by the tester because of chest pain and one patient developed persistent tachycardia and irregular pulse immediately following the test. In 35 tests, the tester instructed the patient to stop walking because of profound oxygen desaturation (SpO(2) <80%). Six patients prematurely terminated the 6MWT because of symptoms. Forty-seven per cent (n = 345) of patients exhibited significant oxygen desaturation (>= 4% fall in SpO(2) to <90%). Pre-exercise SpO(2) was a significant predictor of desaturation in the COPD (1.79, 1.54-2.08, adjusted odds ratio (OR), 95% confidence intervals) and ILD (OR 1.40, 1.11-1.77) cohorts with FEV1 (forced expiratory volume in 1 s) also a predictor in COPD (OR 3.02, 1.77-5.15).Conclusion:Profound oxygen desaturation is the most common adverse event observed during the 6MWT in patients with stable ILD and COPD. We propose that the American Thoracic Society 6MWT guidelines are revised to recommend continuous monitoring of SpO(2) during the 6MWT in patients with ILD and COPD.