A solid-state battery was constructed by interfacing a pressed pellet of poly(o-methoxyaniline), in the emeraldine form with p-toluene sulfonic acid as doping agent, to a magnesium electrode covered with a film of magnesium perchlorate; the contact on the poly(o-methoxyaniline) was done by means of a gold electrode. The so-obtained cell, Mg I magnesium perchlorate I poly(o-methoxyaniline) I gold, was able to supply energy with a power depending on discharge current and on environmental humidity. Values of power up to 2.5 mW cm(-2) at discharge currents of about 2 mA cm(-2) were reached. (C) 1997 Elsevier Science S.A.9013136