Following room‐temperature irradiation of quartz crystals by x rays or &ggr; rays, a transient enhancement of electrical conductivity is observed which decays over a period of several hours. This enhanced conductivity is produced by alkali ions (M+) which are liberated during the irradiation. By freezing in this transient conductivity of synthetic crystals to temperatures below 270 K, the activation energyEmfor migration of free alkali ions alongc‐axis channels of the crystal is shown to be 0.14±0.01 eV. The activation energy for the annealing process is ∼0.5 eV, showing that annealing is not controlled byEm. Results on natural crystals following irradiation are quite different from those of the synthetics; the differences are explained in terms of the presence of shallow traps for free M+ions in natural crystals. Finally, the transient conductivity is compared with other transient phenomena following irradiation, viz., the frequency change and internal friction of quartz‐controlled oscillators.