BACKGROUND: Posttraumatic amnesia (PTA) after traumatic brain injury (TBI) comprises anterograde amnesia (AA), disorientation, and retrograde amnesia (RA). However, RA is often neither assessed nor emphasized. A recent study demonstrated that although AA and disorientation were both present in non-TBI inpatients uniformly taking opioids, RA was absent. This suggests potentially significant utility with RA assessment alone since opioids are commonly prescribed post TBI. METHODS: We compared RA recovery with AA recovery in a prospective cohort post TBI. The Galveston Orientation and Amnesia Test (GOAT) represented a crude test for PTA (GOAT