The main peculiarities of the p–n conversion of the type of conductivity in narrow-band p-Hg1–x Cd x Te solid solutions containing vacancies of mercury upon bombardment by low-energy ions are explained based on the traditional notions about the chemical diffusion of mercury. These peculiarities are related, on the one hand, to the features of the defect formation in Hg0.8Cd0.2Te (containing a small amount of high-mobility interstitial mercury atoms with a great amount of low-mobility vacancies) and, on the other hand, to the high concentrations of intrinsic electrons and holes efficiently screening the electric field of the defect layer. The high conversion rate realized upon ion bombardment, as compared to the conversion rate taking place upon annealing in mercury vapors, is due to the fact that nonequilibrium interstitial mercury atoms are produced in abundance near the surface of the crystal subject to bombardment. This effect depends substantially on the electric field appearing near the outer boundary of the converted layer; therefore, as the Hg content, and, hence, the width of the forbidden band, is increased, one should expect a noticeable decrease in p-n conversion rate.