Exercise capacity can be evaluated in patients with chronic obstructive pulmonary disease (COPD), measuring the distance that patients are able to walk in 6 minutes (six-minute walk distance test; 6WDT). This test is simple to perform, inexpensive, reproducible and safe. It has been frequently employed for the assessment of COPD patients due to its high prognostic value of mortality and its usefulness to evaluate long-term of therapeutic interventions. In severe stages of the disease, the declining results of the best are useful to detect worsening. This review describes the method, standardization and reference values for the 6WDY and the results obtained with different therapeutic interventions, based on data from the literature and from the authors' experience. We also review its predictive value for mortality and its value in the assessment of patients with more severe COPD.