Abstract: A process for solubilizing in water and in aqueous vehicles sparingly water-soluble pharmaceutically active substances, comprising the following operations: 1) forming a complex of the pharmaceutically active substance with a pharmaceutically acceptable non-ionic polymer capable of forming complexes with the substance, and isolating the complex in solid form; 2) dissolving again the thus obtained complex in an aqueous medium by means of a pharmaceutically acceptable surfactant. The method allows to markedly increase the water-solubility of pharmaceutically active organic compounds which are intrinsically poorly or negligibly soluble in water, in order to obtain preparations that are stable in aqueous solution and contain therapeutically and commercially useful concentrations of active ingredient.