Controlled release systems loaded with 2,4-D were prepared by double encapsulation using solvent evaporation technique followed by the complex coacervation method. The production of these systems was aimed at modifying the release rate of the active agent and at reducing the herbicide risks by dermal contact. The coated microspheres are composed of Ethylcellulose or Cellulose acetate butyrate butyryle as microsphere matrix and with Gelatin-Arabic gum complex as envelope. The microparticles were characterized by scanning electron microscopy and the size and size distribution were determined. The drug release from the coated microspheres was established in water at 25 degrees C and it was compared with those of microspheres without envelope. The release mechanism of the active agent from microspheres was investigated according to Fick's law. So the present paper completes the characterization of microspheres by the calcul of the effective diffusion coefficients.