A bilayer device: consisting of a conducting, flexible polypyrrole layer and an adherent, elastic non conducting film was constructed. One end of the bilayer was fixed with a clamp, allowing the electrical contact with polypyrrole. Polypyrrole volume increases and decreases reversibly during electrochemical oxidation and reduction processes in aqueous solutions. Reversible stress gradient across the flexible film promotes reversible angular movements of the free end of the bilayer, around the fixed end. The effect of the anodic and cathodic potential gradients, as well as the effect of the concentration of movable ions on a 180° angular movement, in the electrolytic solution, were studied. Weights of 1000 times the bilayer weight adhered at the bottom of the bilayer were reversibly trailed across 180° by electrochemically controlled oxidation and reduction processes, in a few seconds. As an electric current promotes chemical reactions giving a change of volume and promoting a mechanical energy, the device was named artificial muscle. Similarities and differences between muscles and artificial muscles are discused.