Boswell-Ruys CL, Sturnieks DL, Harvey LA, Sherrington C, Middleton JW, Lord SR. Validity and reliability of assessment tools for measuring unsupported sitting in people with a spinal cord injury. Objectives To develop simple tests to assess the abilities of people with spinal cord injury (SCI) to sit unsupported and to assess the construct validity and test-retest reliability of these tests. Design Cross-sectional comparisons, convenience sample. Setting Biomechanical laboratory. Participants People (N=30) with SCI between the C6 and the L2 level of 2 months to 37 years duration before assessment. The sample was stratified by impairment level (at T8) and time since injury (1y postinjury). Interventions Not applicable. Main Outcome Measures On 2 separate occasions, participants performed tests that measured the distance of upper-body sway and maximal torso leaning, errors made during a coordinated stability task, timed dressing/undressing of the upper body and alternating arm reaching, and percentage change in seated upper body/arm reaching. Results All tests showed good construct validity in that they distinguished between participants with higher (C6-T7) and lower (T8-L2) level impairments (P<.05) and between participants with acute (≤1y) and chronic (>1y) lesions (P<.05). The tests also showed good to excellent test-retest reliability (intraclass correlation coeffiecient3,1 range, .51–.91). Conclusions These simple and quick-to-administer tests have both construct validity and test-retest reliability. They would be appropriate for research and clinical purposes to quantify the abilities of people with SCI to sit unsupported.