To evaluate the reliability and validity of the extended Wheelchair Circuit fifteen dependent subjects with Spinal Cord Injuries performed the extended Wheelchair Circuit two times with 9.3 ± 11.3 days between the trials. Test-retest reliability and validity were calculated for the three outcome measures: ability score, the performance time score and the physical strain score. Validity was assessed by analyzing the scores of the Wheelchair Circuit on age, lesion level and completeness of the lesion. The intraclass correlation coefficients of the Wheelchair Circuit were 0.94 for ability score, 0.99 for performance time score and 0.82 for physical strain score at confidence level p<0.05. Validity was good using lesion level on both ability and performance time scores: a significant difference between scores of persons with para- and tetraplegia was found (p<.05). Age did not correlate with any of the scores and also completeness of the lesion was no factor for wheelchair skill performance. Comparing the original Wheelchair Circuit with the ability score of the extended Wheelchair Circuit showed that the variability and discrimination between subjects and groups improved, but floor and ceiling effect remained. The Extended Wheelchair Circuit is a reliable research tool. The ability and performance time score are valid scores. Further research should focus on validity (especially of the physical strain score) and floor and ceiling-effect reducing tasks using a larger and more varied study population.