Following stroke, locomotion is impaired and strongly associated with ineffective recruitment of paretic leg muscles. Recent investigation in persons with clinically complete spinal cord injury has revealed that locomotor activity in one limb can activate rhythmic locomotor activity in the opposite limb. Although our previous research has demonstrated profound influences of the non-paretic limb on paretic limb motor activity post-stroke, the potency of interlimb pathways for increasing recruitment of the paretic limb motor pattern is unknown. This experiment tested whether there is an increased propensity for rhythmic motor activity in one limb (pedaling limb) to induce rhythmic motor activity in the opposite limb (test limb) in persons post-stroke. Forty-nine subjects with chronic post-stroke hemiparesis and twenty controls pedaled against a constant mechanical load with their pedaling leg while we recorded EMG and pedal forces from the test leg. For the experimental conditions, subjects were instructed to either pedal with their test leg (bilateral pedaling) or rest their test leg while it was either stationary or moved anti-phased (unilateral pedaling). In persons post-stroke, unilateral pedaling activated a complete pattern of rhythmic alternating muscle activity in the non-pedaling, test leg. This effect was most clearly demonstrated in the most severely impaired individuals. In most of the control subjects, unilateral pedaling activated some muscles in the non-pedaling leg weakly, if at all. We propose that, ipsilateral excitatory pathways associated with contralateral pedaling in control subjects are increasingly up-regulated in both legs in persons with hemiparesis as a function of increased hemiparetic severity. This enhancement of interlimb pathways may be of functional importance since contralateral pedaling induced a complete motor pattern of similar amplitude to the bilateral pattern in both the paretic and non-paretic leg of the subjects with severe hemiparesis.