Objective: The 6-min walking test (6 MWT) is commonly used to assess obese patients' aerobic fitness, but it has rarely been compared with a direct measurement of maximal aerobic capacities (VO 2max or VO 2peak) in obese adults. The aim of this study was to investigate the relationship between the distance covered during a 6 MWT with objectively measured VO 2peak and to propose a new equation to predict VO 2peak from this walking test in obese patients. Methods: One hundred and thirty-seven obese patients (45.6 ± 12.5 years) admitted to our hospital for a multidisciplinary rehabilitation program were enrolled. After assessment of their body composition, the participants were asked to perform a 6 MWT and their maximal aerobic capacities (VO 2peak) were measured. Result: There is a significant linear relation between VO 2peak and the distance covered during the 6 MWT (p < 0.001; r ¼ 0.349). The determinant of VO 2peak was body mass index, waist-to-hip ratio, fat free mass, leading to the follow prediction equation VO 2peak such as VO 2peak (l/min) ¼ (body mass index  0.0150065) À (waist-to-hip-ratio  0.8595088) þ (fat-free-mass  0.0295478) þ (6-min walk test  0.0020672) À 0.5853372. Conclusion: The 6-min walk test is a reliable method to reflect obese women's aerobic capacities and the distance covered can be used to accurately estimate VO 2peak according to our newly proposed equation. ä IMPLICATION FOR REHABILITATION Obesity is a worldwide disease and physical capacity evaluation is a key point for rehabilitation. The six minutes' walk test is commonly used in obese people to assess aerobic fitness. This study proposes a new equation using 6 MWT performance to estimate VO 2peak .