Contrast enhancement simulating an abscess or residual tumor has been described in postoperative cranial computed tomography (CT) scans. This study was undertaken to determine the cause of this contrast enhancement by using canine brain as an experimental model. Sequential CT scanning was performed with and without contrast enhancement following partial resection of the right hemisphere, and the CT findings were correlated with the histological changes. Findings indicate that enhancement of the surgical margin is related both temporally and spatially to the neovascularity following surgery. The ring-like enhancement around the surgical margin is seen best at two to four weeks after surgery, and may simulate an abscess. However, edema seen around an abscess in adjacent brain is absent or minimal in the case of postoperative enhancement during this period, and this feature should help differentiate these entities.