The interpeduncular nucleus (ITP) of man has been studied from a human brain impregnated "in toto" by the Golgi method. A wax model reconstructed from serial sections gives information on its size, its shape and its position within the brain. Its volume was also calculated. It overlies the interpeduncular cistern where is one of the major confluences of cerebrospinal fluid and blood vessels. The types of cells impregnated and their relationship to blood vessels and the underpial ventral surface are illustrated. In the ITP of man there are morphologic elements which do not exclude the possibility, at least for a portion of it, of a neurohormonal means of communication which could be exerted through the cerebrospinal fluid and blood vessels.