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Activities done prior to formulation development are called as preformulation studies. It provides the scientific basis for formulation development. Preformulation studies can be broadly classified into two classes - (i) fundamental properties and (ii) derived properties. Fundamental preformulation properties are specific to the drug molecule and are dependent on the chemical structure of the drug molecule. In contrast, derived preformulation pre-formulation properties are carried out to learn about the issues related to development of a particular dosage form like solid oral, liquid oral or parenteral. Fundamental preformulation properties include - Solubility, dissociation constant (pKa), salt formation, partition or distribution coefficient, pH solubility profile and dissolution kinetics, permeability, solid state properties like polymorphism, stability profile etc. Derived preformulation properties are specific to the intended dosage form to be developed. The last activity performed in pre-formulation studies is the compatibility studies, wherein the physical and chemical stability of the drug molecule is studied in presence of excipients. Obviously, the choice of excipients is dictated by the type of dosage form to be developed. By comparing the physicochemical properties of each drug candidate with in a therapeutic group, the preformulation scientist can assist the synthetic chemist to identify the optimum molecule, provide the biologist with suitable vehicles to elicit pharmacological response and advise the bulk chemist about the selection and production of the best salt with appropriate particle size and morphology for subsequent processing. [ABSTRACT FROM AUTHOR]