Microspheres loaded by pesticide model were prepared by solvent-evaporation technique and double encapsulation using solvent evaporation technique followed by complex coacervation method in Gelatin-Arabic gum. Various matrixes were used such as Ethylcellulose, Cellulose acetate butyrate butyryl and polymethylmethacrylate. The microparticles were characterised by scanning electron microscopy and infrared spectroscopy and the size and size distribution were determined. The drug release was established in water at 25 degrees C and the effects of nature of the matrix, the double encapsulation and some of the process parameters such as stirring speed, polymer-solvent, drug-polymer ratios and percentage of emulsifier on the drug loaded and released were studied. The release mechanism of the active agent from microspheres was investigated according to Fick's law and the effective diffusion coefficients were calculated. (c) 2006 Elsevier B.V All rights reserved.