Abstract: A process for the preparation of Poly DL-lactide-co-glycolide nanoparticles having antitubercular drugs encapsulated therein comprising: (i) preparation of an aqueous solution of stable water soluble drugs in DW/NS/PBS (ii) preparation of unstable drugs in DW/NS/PBS (iii) preparation of a polymer and hydrophobic drug solution in an organic solvent, (iv) mixing separately the solutions of steps (i) and (ii) with that of step (iii) and sonicating under cold conditions, (v) adding the above emulsion to aqueous PVA and resonicating under cold conditions, (vi) stirring the emulsion 0nd centrifuging the same (vii) washing the said particles, reconstituting the same and lyophilizing.