Methods have been developed for the quantitative evaluation of the canine brain using computed tomography (CT). Sixteen studies in 10 adult Beagle dogs were used to define the precision for densitometry and dynamic studies in the normal canine brain. For various regions of the brain, intraanimal and interanimal variability was determined for normal tissue CT number, contrast enhancement, and parameters relating to blood flow and blood volume. High precision was obtained for densitometry both within and among animals when evaluated over a 9 month period. Both intra- and interanimal variability in dynamic measurements was relatively large between studies, but hemispheric comparisons within a given study and between studies showed high precision. These methods can be used to evaluate morphologic and physiologic changes in the canine brain following radiation or other cytotoxic treatments.