The purpose of this study was to demonstrate the course of infantile neuronal ceroid-lipofuscinosis with brain magnetic resonance imaging (MRI) in children aged 3 months to 11 years. Twenty-one patients and 46 neurologically normal controls of the same age were examined. The images were evaluated visually; then signal intensities were measured and related to those of references. MRI abnormalities were detectable before clinical symptoms. The radiologic picture of the brain varied with the duration of the disease. Pathognomonic MRI findings in the early stage of the disease were generalized cerebral atrophy, strong thalamic hypointensity to the white matter and to the basal ganglia, and thin periventricular high-signal rims from 13 months onward on T2-weighted images. In patients over 4 years old, cerebral atrophy was extreme, and the signal intensity of the entire white matter was higher than that of the gray matter, which is the reverse of normal. This study showed that the abnormalities seen on MRI progress rapidly during the first 4 years of life, then stabilize, in conformity with the clinical and histopathologic pictures of infantile neuronal ceroid-lipofuscinosis.