Hemoglobin (Hb) embedded in lactobionic acid (LA) film can give a pair of stable, well-defined, and quasi-reversible cyclic voltammetric peaks, located at the potential characteristic of the heme Fe(III)/Fe(II) redox couple. The formal potential of the protein in LA film was -209mV. The apparent heterogeneous electron transfer rate constant and the number of protons concomitant per electron during the electron transfer process have been calculated. Hydrogen peroxide could also be catalytically reduced by the protein in LA film. (c) 2005 Society of Chemical Industry.