Intracerebral inoculation of Trypanosoma b. brucei and T. b. rhodesiense into suckling mice produced infection of brain tissue which subsequently gave rise to an infection of the blood and other tissues, in which a normal histopathological picture was observed. Treatment of other intracerebrally infected sucklings with 5 mg/kg diminazene aceturate (Berenil) to clear the infection from the blood permitted a study of the course of the infection in the brain without interference from pathological processes induced by bloodstream infections. There was rapid multiplication and migration of trypanosomes throughout the brain of mice. Pathological processes normally seen in experimental central nervous system infections were absent, except in a single mouse treated earlier with Berenil which developed meningo-encephalitis with trypanosomes present in the choroid plexus. The possible use of such a model system in chemotherapeutic studies is discussed.