The authors investigate the thermal insulation of plasmas in Tokamak-3, taking as thermal insulation parameter the energy confinement time ofthe plasma τE and relating it to the discharge parameters: the stabilizing magnetic field Hz, the charged particle density ne and the discharge current I. It is found that for ne ≥ 2 × l013 cm−3 τE is virtually independent of Hz, for ne = (l-5) × 1013 cm−3 τE increases somewhat with ne and in proportion to I. The experimental results fit the empirical formula τE∼a2Hφ.