A pharmaceutical composition is disclosed comprising a fat emulsion containing microspheres and having its electric charge adjusted to a negative value and a biologically active substance selected from the group consisting of a basic peptide and a basic protein, which biologically active substance is adsorbed to the microspheres in the fat emulsion. An acidic phospholipid, a fatty acid, a bilic acid and a salt of such substances is preferred as an agent for adjusting the electric charge of the fat emulsion. Motilin derivatives, vasoactive intestinal polypeptide derivatives and calcitonin are preferred biologically active substances.