Over 45% of registered drug substances and 75% being in development are described as practically insoluble. With regard to the to design of oral dosage forms, solubility and bioavailability improvement are issues. It can be achieved by particle size reduction, polymorph transition, preparation of solid dispersions. The formation of binary systems and amorphization are an interesting research topic. Short-range molecular order, high molecular mobility, excess free energy are characteristic features of amorphous drug substances that provide solubility improvement. The methods of solid dispersion preparation include melting, mechanical disruption of crystal lattice, solvent evaporation and supercritical CO2 technology. In recent years, also co-amorphous systems have attracted particular attention. They contains a low molecular weight carrier or other drug substance. Although limited stability of disordered systems and possibility of spontaneous crystallization upon storage (effect of temperature, pressure, humidity) stay as limitation they do not inhibit work on the commercialization of amorphous drug products.