The transformation of the stable crystalline form can enhance the bioavailability of poorly water soluble drugs. The molecular dispersion, or solid solution, can be formed by various methods. The thermodynamic and kinetic properties of such compounds are very similar to the amorphous state. Twin-screw melt-extrusion, with controlled pressure, heat and shear stress, is a powerful way for separating the molecules of the active ingredient from each other and distributing them in the matrix homogenously. The extrudate can be processed onward immediately after a required cooling phase. The dependence of the possible effect of extrusion on the process parameters was investigated by Raman-microscopy and X-ray powder diffraction in course of the preparation of solid solution of spironolactone.