Results of research on the magnetic susceptibility of nonstoichiometric compounds of group IV and V transition d-metals are generalized. It is shown that nonstoichiometry-related susceptibility changes in transition metal carbides are associated with the peculiarities of the electron energy spectra in carbides. The immediate cause for the reduced susceptibility of nonstoichiometric carbides during atomic-vacancy ordering is the change in the contribution from orbital paramagnetism, due to short-range ordering. A possibility to employ the magnetic susceptibility for estimating short- and long-range order parameters and determining the superstructure type in nonstoichiometric compounds is discussed.