To investigate the effects of exercise training on ventilatory efficiency and physiological responses to submaximal exercise in subjects with small abdominal aortic aneurysm (AAA). Sixty-five male patients (72.3 ± 7.0 years) were randomized to exercise training (n = 33) or usual care group (n = 32). Exercise subjects participated in a training groups for 3 mo. Cardiopulmonary exercise testing was performed before and after the study period and peak (Equation is included in full-text article.)O2, the ventilatory threshold (VT), the oxygen uptake efficiency slope (OUES), and the (Equation is included in full-text article.)E2/(Equation is included in full-text article.)CO2 slope were identified. Baseline work rates at VT were matched to examine cardiopulmonary responses after training. Significant interactions indicating improvements before and after training in the exercise group were noted for time (P < .01), (Equation is included in full-text article.)O2 (P < .01), and work rate (P < .01) at the VT. At peak effort, significant interactions were noted for time (P < .01) and work rate (P < .01), while borderline significance was noted for absolute (P = .07) and relative (P = .04) (Equation is included in full-text article.)O2. Significant interactions were observed for the OUES both when using all exercise data (P = .04) and when calculated up to the VT (P < .01). For the (Equation is included in full-text article.)E2/(Equation is included in full-text article.)CO2 slope, significance was noted only when calculated up to the VT (P = .04). After training, heart rate, (Equation is included in full-text article.)E, (Equation is included in full-text article.)O2 and respiratory exchange ratio were significantly attenuated for the same baseline work rate only in the exercise group (all P < .01). Exercise training improves ventilatory efficiency in patients with small AAA. In addition, patients who exercised exhibited less demanding cardiorespiratory responses to submaximal effort.