New solid forms with modified physicochemical and biopharmaceutical properties can be obtained by introducing different guest molecules to form cocrystals or salts.This approach appears to be an advantageous alternative for pharmaceutical research and development.Inspired by the newly released Guidance for Industry：Regulatory Classification of Pharmaceutical Cocrystals,we reviewed the differences between cocrystals and salts in their definition,structure,characterization,regulatory issues and physicochemical properties such as solubility,stability as well as bioavailability.In addition,some newly developed techniques for characterizing cocrystals or salts are also introduced.