The present study was designed to assess differences in compartmental contributions to ventilation between cycle pedaling and treadmill walking. Eight subjects performed submaximal cycle (CE) and treadmill (TM) exercise. The mean maximal work loads were not significantly different between the 2 modes of exercise. Ventilation (VE), oxygen uptake (VO2), and respiratory inductance plethysmography (RIP) were measured continuously during both modes of exercise. During both TM and CE, VE measured by RIP was found to correlate significantly with VE measured by pneumotachometer. Although the ventilation/work load relationship for CE exceeded that for TM in all subjects, when changes in rib cage (RC) and abdominal (ABD) tidal volume responses were expressed relative to changes in VE, no significant differences were found between TM and CE (RC, p greater than 0.05; ABD, p greater than 0.05). When these changes in tidal volume were expressed relative to changes in work load and independent of ventilation, there were no significant differences between separate compartmental responses during TM or CE (RC, p greater than 0.05; ABD, p greater than 0.05). We conclude that while absolute degrees of ventilation at a given work load differ between cycling and walking, the postural and ventilatory differences between these forms of exercise do not appear to induce differences in the relative contributions of the rib cage or the abdomen to tidal breathing.