The processes of the preparation of highly conductive polymer composites of poly(methyl methacrylate) and polypyrrole (PMMA/PPy) have been studied. The composites were prepared by a chemical modification method resulting in a network-like structure of polypyrrole embedded in the insulating polymer matrix. Water was used as a solvent. The content of polypyrrole was determined by elemental analysis varying from 0.25 to 10 wt%. The electrical conductivity of compression-moulded samples depends on the concentration of polypyrrole and reached values of between 1 x 10(-9) S/cm to 0.1 S/cm. Highly conductive composites were also obtained from a mixture of coated and non-coated PMMA particles. The PMMA/PPy composites were characterized by elemental analysis, infrared spectroscopy and X-ray photoelectron spectroscopy (X.p.s.). The method of low-voltage scanning electron microscopy was used to study the potential contrast in dependence on the acceleration voltage between areas of different chemical composition. This method can be used to show the perfection of the PPy network structure in the composites. The antistatic properties of PMMA/PPy composites were demonstrated. The stabilizing effect of PPy on the thermal stability of poly(methyl methacrylate) was shown by thermogravimetric analysis.