It is shown that the production rate of electron traps during fast neutron bombardment of graphite can be determined by comparing its properties with those of chemically doped graphite. A value of 9 × 10−5 trap per equivalent megawatt day unit of reactor bombardment is obtained. This comparison also shows how the scattering of the carriers is affected by bombardment. The validity of the conclusions which are reached depends upon certain assumptions concerning anisotropy and heterogeneity, which are explored in rather considerable detail.