Evidence from Leonardo da Vinci's artistic and scientific work is presented and corroborates Freud's conclusion that this greatest of artists suffered from the consequences of severe disturbances in psychosexual development. His surviving works and biographical writings permit one to speculate that sublimation of his aggressive instinctual drive had taken place to a much greater degree than had sublimation of his erotic instinctual drive. It is possible that the energy necessary for his prodigious productivity may have originated primarily from aggressive rather than from erotic instinctual sources. Further studies are needed in order that the various parameters of this problem be adequately explored.