Injectable drug laden microspheres are obtained from unsaturated functionalized polyhydric alcohol ester of polyester by a method comprising dissolving the unsaturated functionalized ester in a hydrophobic organic solvent, dissolving drug and/or biologically active agent in water, admixing the two solutions to form water-in-oil emulsion, forming an aqueous solution of stabilizer, admixing the water-in-oil emulsion and the stabilizer solution to form water-in-oil-in-water emulsion, and evaporating the organic solvent.