35S-Hemineurine penetrated across the blood-brain barrier more rapidly than 35S-thiamin within the first 30 min after intravenous administration. Within 24 hrs content of 35S-thiamin in the neurones exceeded by 34% its concentration in glia and by 200% -- in myelin fraction. 35S-Hemineurine was bound slightly with brain proteins as compared with thiamin and it was removed at the higher rate from brain regions and subcellular structures.