Objective: To investigate whether dyspnea on exertion in otherwise healthy obese women was associated with an increase in the oxygen cost of breathing or cardiovascular deconditioning. Methods: Obese women with and without dyspnea on exertion participated in two independent experiments (n=16 and n=14). All participants underwent pulmonary function testing, hydrostatic weighing, ratings of perceived breathlessness during cycling at 60 W, and determination of the oxygen cost of breathing during eucapnic voluntary hyperpnea at 40 and 60 L/min. Cardiovascular exercise capacity, fat distribution, and respiratory mechanics were determined in 14 women in experiment two. Data were analyzed between groups by independent t-test and the relationship between the variables was determined by regression analysis. Measurements and Main Results: In both experiments, breathlessness during 60 W cycling was markedly increased in over 37% of the obese women (p<0.01). Age, height, weight, lung function, and %body fat were not different between the groups in either experiment. In contrast, the oxygen cost of breathing was significantly (p<0.01) and markedly (38-70%) greater in the obese women with dyspnea on exertion. The oxygen cost of breathing was significantly (p<0.001) correlated with the RPB obtained during the 60 W exercise in experiment one (r²=0.57) and two (r²=0.72). Peak cardiovascular exercise capacity, fat distribution and respiratory mechanics were not different between groups in experiment two. Conclusions: Dyspnea on exertion is prevalent in otherwise healthy obese women, which appears strongly associated with an increased oxygen cost of breathing. Exercise capacity is not reduced in obese women with dyspnea on exertion.