Abstract: A theory of catalytic currents at a tubular electrode has been developed. The theory was applied to the catalytic currents observed in the reduction of ferric ions at the tubular gold electrode in the presence of hydrogen peroxide. The results showed that the diffusion coefficient and rate constant of the chemical reaction are 4.6×10^-6cm²/sec and 105.8lit/mol·sec, respectively, in our experiments. Experimental data are in good agreement with the theory.