Pharmaceutical cocrystals,or the hydrogen-bonded crystalline complex between an API and a benign co-former (preferably from the GRAS list),offer rational approaches to make new supramolecular entities for drug deliver and formulation.Crystal engineering principles for cocrystal synthesis through robust heterosynthons have been developed for drugs containing carboxylic acid,carboxarnide,sulfonamide,alcohol,amine functional groups with complementary co-formers such as pyridine,pyridine-N-oxide,acid,amide,etc.A major advantage of cocrystals over traditional salts is that APIs containing non-ionizable functional groups are amenable to solid-state control and modification of properties,such as hydration,ambient stability,dissolution,color,tableting.Moreover,cocrystals offer a way to control polymorphism discovered at late stages for an active lead or a marketed drug.Examples of bioavailability improvement for anti-fungal & anti-bacterial drugs and an SNRI inhibitor,and stability improvement for an anti-cancer drug in cocrystal adducts will be shown.From a preparative viewpoint,solution crystallization,solvent-less and solvent-drop grinding,ultrasonication,slurry crystallization,etc.can be used,also in high-throughput automated crystallization set-ups.Pharmaceutical cocrystals are the new paradigm in novel medicines.