The existence of an homogenity range of BaCu1+yO2+x in respect of copper was established by EMF measurement and DTA, and the nonstoichiometry index (x(t)) of oxygen versus temperature (t) was measured by TC in static dry oxygen. The values obtained for x and y were : 0 less than or equal to y(+/- 0.02)less than or equal to 0.15 0.05 (1000 degrees C) less than or equal to x(t)(pO(2) = 1 atm, y = 0.15) +/- 0.03 < 0.25 (450 degrees C) significant attention was paid to phase and composition analysis of samples synthesized.