The invention concerns microcapsules with prolonged release of active principles with low solubility, consisting of a core containing the active principle and coated with a polymer layer which controls the release of the active principle. The aim is that said oral microcapsules containing hardly soluble active principles, should have a coating film of sufficient thickness to ensure controlled permeability and should be adapted to industrial reproduction. This is achieved by the inventive microcapsules of mean diameter less than 1000 microns, and whereof the coating film contains a film-formingpolymer (P1) insoluble in gastrointestinal tract fluids, a water-soluble polymer (P2), a plasticizer (PL), and optionally a lubricating surfactant (TA). Said microcapsules are characterized in that their coating films represents at least 3 % p/p of dry matter, relative to their total weight and their core contains a hardly soluble active principle and a solubilizing agent (polyoxyethylene hydrogenated castor oil) which provides the core wherein it is contained with properties such that the behaviour of the exposed core (non-coated) in a given dissolving test (TD), is as follows: release of 80%of active principle in less than two hours. The invention also concerns the use of such microcapsules in galenic formulation.