OBJECTIVE: Computed tomographic (CT) scanning can reveal the pattern and severity of structural brain damage after head injury. With the proliferation of CT scanners in general hospitals, and with improvements in patient transport, the interval from injury to the first CT scan is decreasing. The potential result is an “admission” scan missing an evolving and potentially operable lesion. Furthermore, the literature is confusing regarding the timing and coding of CT findings. We sought to establish the frequency of deterioration in CT appearance from an admission scan to subsequent scans and the prognostic significance of such deterioration.