Clinical trials of experimental neuroprotective and neuroregenerative therapies for acute spinal cord injury (SCI) typically require large numbers of patients to be enrolled. An important factor in designing such trials is the number of patients that can be realistically recruited at a given institution. The total number of patients with acute SCI treated at a neurotrauma centre is typically considered when such a site becomes a recruiting centre for a clinical trial. However, only a fraction of patients may be truly eligible due to the inclusion and exclusion criteria of the trial. This study was conducted to estimate the proportion of patients with acute SCI who would theoretically satisfy basic inclusion criteria for such a hypothetical clinical trial. Using a local prospective database, we reviewed 406 patients with acute traumatic SCI admitted between 2005 and 2009. 259 of 406 patients (64%) presented within 12 hours of injury, 53 patients (13%) between 12 hours and 24 hours, and 30 patients (7%) between 24 hours and 48 hours. Patients were assessed on admission using the American Spinal Injury Association Impairment Scale: category A, 39% of patients; B, 11%; C, 17%; and D, 28%. The number of patients who presented with injuries or other conditions that would likely exclude them from enrolment was 30%. Thus, of a total of 406 patients with SCI admitted over four years, the number who would have been eligible for an acute clinical trial was disappointingly small. This study is the first to quantify this challenging aspect of conducting acute SCI clinical trials, and provides guidance for those planning such initiatives.