Study design: Secondary analysis of prospectively collected observational data. Objectives: To assess the representativeness of the Spinal Cord Injury Model Systems National Database (SCIMS-NDB) of all adults aged 18 years or older receiving inpatient rehabilitation in the United States (US) for new onset traumatic spinal cord injury (TSCI). Setting: Inpatient rehabilitation centers in the US. Methods: We compared demographic, functional status, and injury characteristics (nine categorical variables comprising of 46 categories and two continuous variables) between the SCIMS-NDB (N = 5969) and UDS-PRO/eRehabData (N = 99,142) cases discharged from inpatient rehabilitation in 2000-2010. Results: There are negligible differences (<5%) between SCIMS-NDB patients and the population for 31 of the 48 comparisons. Minor differences (5-10%) exist for age categories, sex, race/ethnicity, marital status, FIM Motor score, and time from injury to rehabilitation admission. Important differences (>10%) exist in mean age and preinjury occupational status; the SCIMS-NDB sample was younger and included a higher percentage of individuals who were employed (62.7 vs. 41.7%) and fewer who were retired (10.2 vs. 36.1%). Conclusions: Adults in the SCIMS-NDB are largely representative of the population of adults receiving inpatient rehabilitation for new onset TSCI in the US. However, users of the SCIMS-NDB may need to adjust statistically for differences in age and preinjury occupational status to improve generalizability of findings.