Context: Functional outcome in relation to CT findings in traumatic brain injured (TBI) patients is not well established in relation to cognitive and vocational outcome. Objective: To investigate the possible correlation between relatively simple quantitative radiological measurements and cognitive and vocational outcome. Design: Retrospective analysis of quantitative assessment of CT studies in relation to post-injury cognitive changes and vocational outcome. Setting: US Army Medical Centre. Patients: 74 penetrating head injured (PHI) and 37 closed head injured (CHI) Vietnam war veterans. Outcome measures: The Armed Forces Qualification Test (AFQT); Disability score; Return to work. Results: Total brain volume loss, third ventricle width (3VW), ventricular score (VS), and septum-caudate distance (SCD) were significantly related to cognitive change and return to work in PHI patients. Volume loss and 3VW were the most valuable radiologic predictors of outcome in multivariate linear and logistic regression models for both CHI and PHI. Conclusion: 3VW on late CT scans following traumatic brain injury is a powerful predictor of overall long-term cognitive outcomes and potential for return to work.