Aim <p>Individuals with spinal cord injury (SCI) have an increased prevalence of orthostatic hypotension (OH). Diagnosis of OH is made with active standing or tilt table testing, with limited the use in individuals with SCI.</p> Methods <p>An alternative approach to assess OH is the sit-up test, which involves passive repositioning from the supine to the seated position. The purpose of this study was to document the reliability and validity of the sit-up test, and determine whether the level or severity of injury related to orthostatic blood pressure (BP) responses in a large, diverse group of individuals with SCI.</p> Results <p>A total of 166 participants—119 individuals with SCI and 47 uninjured control—completed two sit-up tests, and 36 individuals who completed the sit-up tests also underwent a head-up tilt test. Change in BP from sit-up test 1 to sit-up test 2 was not significantly different for either systolic BP or diastolic BP. Neither level nor severity of injury contributed to the reliability assessments, which showed disappointing results with generally low interclass correlation coefficients (ICC), with values ranging from 0 to 0.63, and large standard error of measurements (SEM), ranging from 5.2 to 13.7 mmHg. Comparison between BP responses to the sit-up test and the head-up tilt showed good sensitivity and specificity, with positive predictive values &gt; 75%.</p> Conclusion <p>Prevalent BP instability likely contributed to the poor reliability of the sit-up test, but the test is easy to perform with a high likelihood ratio for the valid assessment of OH in individuals with SCI.</p> <p><b>Clinical trial registration: </b>NCT01758692</p>