Experiments on annealing of CdGeAs2-, CdSnAs2- and ZnGeP2-crystals in the vapor of volatile constituents were carried out. Conductivity and Hall effect measurements were performed to characterize the modification of electrical properties, caused by the interaction of the crystal with the gas phase during annealing. Literature data and the results of the present work are discussed based on the results of a quasi-chemical analysis. This yielded that the results of annealing depends essentially on both the conditions of the experiment and the initial imperfection of the crystal. The most probable native structural defects becoming apparent under the annealing were the following: for CdSnAs2 - SnCd, VAs; for CdGeAs2 - VAs, VCd, CdGe, GeCd; for CdSiAs2 - SiAs, VAs ; for CdSiP2 - VCd, VP; for ZnGeP2 - ZnGe, GeZn, VZn, VP; and for ZnSnP2- ZnSn, SnZn, VZn, VP.