The oxidation of I- to IO3- in acidic media occurs at numerous electrode materials at potential values corresponding to the anodic discharge of H2O With simultaneous evolution of oxygen. In the study reported here the anodic current density for IO3- production was measured by difference voltammetry at rotated disc electrodes (r.d.e.’s) constucted from pure glassy carbon (GC) and Kelgraf (graphite plus Kel-F) composite materials. These signal values (S) were normalized relative to the background current (B) for oxygen evolution measured at 1.75 V vs SCE, a potential corresponding to the transport-limited production of IO3- at GC. Despite a small positive shift in E1/2 with decreasing fractional active area, the signal-to-background ratio (S/B) at the Kelgraf electrodes was enhanced relative to that for the GC electrode. For example, S/B at a 2% Kelgraf r.d.e. was nine times larger than at a GC r.d.e. This corresponds to an increase in current efficiency (S/(S + B)) for IO3- production from about 50% at the GC r.d.e. to about 90% at 2% Kelgraf r.d.e. This is explained on the basis of (i) a significant decrease in total background current as a result of the decreased fraction of the Kelgraf surface that corresponds to carbon, and (ii) a larger flux density of I- at the carbon microelectrodes in the Kelgraf r.d.e., as compared to the GC r.d.e., as a result of radial diffusion, i.e. the so-called ’edge effect’.