Four pyrolyzed carbonaceous materials were reacted with 950 ppm of nitric oxide (in N-2) in an entrained flow furnace at temperatures between 800 and 1.000degreesC. Their apparent reactivities, corrected for mass transfer, when calculated on a BET area basis displayed a wide spread of values. However when recalculated for the surface area estimated for pores greater than 20 nm in size, as measured by mercury porosimetry, far better agreement was obtained. The results are consistent with other data in the literature, for which equivalent surface areas were available.