It is shown that the mechanism of high-temperature superconductivity in oxygen-deficient perovskites, based on a cooperative Jahn-Teller effect for Cu2+ions, allows the dependence of the critical temperatureTcon oxygen content to be calculated. This dependence qualitatively accounts for the experimental data in the case of YBa2Cu3O2and the maximum predicted forTcis consistent with that deduced from structural data.