More than 50％ of marketed drugs and 90％ drug candidates are believed to be poorly water-soluble,and these figures keep growing due to input of new drug entities into the pool,thanks to the fast development in drug discovery.It has long been recognized that poor solubility poses problems of retarded dissolution rate and thereby poor bioavailability.Enhancement of dissolution and oral bioavailability remains a challenge not only in formulation but also for early-stage development despite years of efforts and progress.According to the canonical Noyes-Whitney equation,the dissolution rate of drug crystals or particles is positively proportionate to the solubility and the surface area of a specific drug entity1.Based on this rationale,efforts have been made in the past to increase inherent solubility and surface area or dispersity of drug entities.Optional strategies include,but not limited to,salt formation,microsizing or nanosizing,solid dispersion,amorphorization and inclusion complexation2.While improving dissolution works very well for enhancement of oral bioavailability of BCS Ⅱ drugs,it fails for BCS Ⅳ drugs whose oral absorption calls for enhancement of dissolution and permeation across gastrointestinal biomembrane simultaneously1.In the past decades,novel approaches have been investigated towards this end.This area continues to be active with new methods and theories proposed and put into practice.In this special issue,webring together prominent scientists to showcase the most recent advances in the big field of enhancement of dissolution and oral bioavailability.