A cyclic voltammetric study of the electrochemistry and chemical stability of the poly(vinylferrocene) (PVFc) redox couple, coated on a gold substrate, in aqueous solutions of H2SO4, HClO4 and HCl was carried out. It was found that the anodic peak potential (E pa) did not depend on the acid concentration in the range (1.0×10−2 to 1.0×10−7 molL−1). However, the E pa values shifted linearly to less positive potentials when investigated in more concentrated acid solutions in the range 1–5molL−1. The slope of the E pa versus acid concentration graph was found to be in the order H2SO4 >HCl>HClO4. In this regard PVFc behaved very similar to 1,1′-bis(11-mercaptoundecyl)ferrocene (Fc(C11SH)2) except for its chemical stability. In H2SO4 media the PVFc was found to be much less stable than 1,1′-Fc(C11SH)2. The dependence of E pa on acid concentration could be used to monitor state of charge of lead-acid batteries. However, for this application Fc(C11SH)2 would be a better choice because of its superior chemical stability.