Objectives:To determine the measurement properties of the Galveston Orientation and Amnesia Test (GOAT) using the Rasch model and rating scale analysis (RSA).Design:Calibration of data collected weekly during rehabilitation.Setting:Six inpatient rehabilitation facilities.Participants:77 patients admitted for their first rehabilitation after traumatic brain injury.Results:Rescoring the items as dichotomies, three strata of posttraumatic amnesia (PTA) were identified. All items cohered to define a single construct and the item hierarchy confirmed their hypothesized ordering.Conclusions:Equal-interval measures of PTA were developed that exhibited good reliability and validity. A self-scoring key was developed to more efficiently assess PTA.