The authors present the results of experimental studies on a discharge in the Tokamak-6 device with a specific instability whose appearance coincides with a sudden jump in the transverse energy of the plasma. It is shown that in these discharge regimes the current is carried by a relatively small group of runaway electrons with energies of 10 - 500 keV, while the main plasma with e ≃ 3 × 1012 cm−3 has a low temperature (Te, Ti ∼ 10 eV) and carries practically no current. Preionization of the working gas or the introduction of a relatively small (∼ 2 – 3%) local inhomogeneity in the longitudinal magnetic field converts these runaway discharges into normal Tokamak discharges.