Seven neonatal dogs were inoculated intracerebrally with Avian Sarcoma Virus (ASV) and studied by computed tomography (CT) for intracranial tumors. The tumor yield was five anaplastic astrocytomas and two sarcomas, with an average latency of 57 days. Computed tomography accurately detected all tumors over 5 mm in diameter and predicted the size of the tumors within 3 mm. The intensity of contrast enhancement was directly related to the dose of Conray-60. The area of enhancement on the CT scan correlated precisely with tumor permeability as determined histologically with horseradish peroxidase (HRP). Edema seen in CT scans correlated well with edema present in histological sections. Peritumoral edema was impermeable to both Conray-60 and HRP. The ASV-induced canine brain tumor model appears well suited for future CT studies.