The variation of reactivity along and across the carbon lattice was studied on flat specimens of pyrographite of various thicknesses. The basal planes used were either the surface of carbon or one parallel to it obtained by splitting thicker specimens, while the end planes were the side faces of the crystallites as obtained in cutting the specimens. Investigations were carried out in the temperature range up to 1600ยฐK in a resistance furnace with preheating of the reacting gas and at higher temperatures in a highfrequency induction furnace without preheating. The constants of the reaction rate on the basal plane K,, and on the side faces of the crystallites (end faces of the plates) K,, were determined using the data on the variation in the weight and size of the specimen. An exponential relationship with inverse of temperature was found for the variation of the specific reaction rate in an atmosphere of carbon dioxide for both types of faces. In the temperature range below 1700ยฐK the ratio K,/K, lies between 30 and 45, while at temperatures above 1800ยฐK is found to be as low as 3 to 4 and exhibits little dependence on temperature. A drastic change in K,/K, occurs at temperatures from 1500 to 18OO"K, which correspond to an appreciable diffusion retardation on the side faces of the crystals and kinetic conditions on the basal planes. It is shown that the difference in the reaction rates on the side faces of the crystallites and the basal plane depends on the number of structure defects in the basal plane.