The present study was aimed at investigating the use of a treadmill for ambulation training of paraplegic subjects. To investigate the likely eectiveness of this modality of rehabilitation, six paraplegic patients (three male and three female) were studied, using new generation reciprocating gait orthoses (RGO and ARGO), in a treadmill training program. Oxygen consumption, heart rate, and pulmonary ventilation were measured when the subjects were walking at their most comfortable speed on the treadmill and on the open ®eld. These measurements were carried out at the beginning of the study and after two and six months of treadmill training. The following ®ndings were signi®cant: the treadmill walking required 30% less energy than open ®eld ambulation prior to training (P50.001) and 50% after training (P50.05). The most comfortable walking speed was faster on the treadmill than on the open ®eld by 18% prior to training (P50.05) and 42% afterwards (P50.05). The energy cost was 50% less after 2 months training on the treadmill (P50.05) showing that treadmill training can improve the eciency of over ground ambulation. It can be concluded that the treadmill training improves the RGO/ARGO walking capability, probably both the walking eciency (short term adaptation) and physical ®tness (long term adaptation).