The maximal physical activity capacity of children operated on for tracheoesophageal fistula (TEF) has not been clearly defined. Eight patients (average age, 12 years) successfully operated on for TEF at birth underwent maximal exercise stress testing on a treadmill, according to the Bruce protocol, to test physical work capacity. Heart rate (HR), oxygen consumption (VO2), and pulmonary ventilation (VE) were measured by a portable lightweight telemetric device. Nine healthy children served as controls. Exercise duration was significantly lower for TEF subjects than for controls (11.6 +/- 1.7 minutes v 15.1 +/- 2.3 minutes; P < .01). Mean HR at rest and during exercise did not differ between the groups. All children reached the maximum HR according to their age; however, for the majority of TEF patients, this occurred at an earlier stage than in the controls. No differences were seen in mean VO2 at rest and on exertion between TEF and control children. However, maximal VO2, as measured at the end of exercise, was significantly different when normalized per kilogram of body weight (VO2/kg = 52.3 +/- 5.8 v 33.3 +/- 6.6; P < .005). The physical rehabilitation of TEF children usually takes into account only respiratory and nutritional factors. However, complete assessment of their cardiac and respiratory function, at rest and on exertion, also should be performed, because this may show that some patients have reduced motor performance; evidence is now accumulating that these children can safely participate in the same physical activities of their healthy peers.