EPR spectra of five compounds of Y 1-x Pr x Ba 2 Cu 3 O 7 with x = 0.0, 0.08, 0.20, 0.50, 1.00 are reported. Different types of spectra are observed after deoxygenation. The most important feature is the occurrence of the 4-line spectra (to which we assigned an electronic spin S = 2) obtained through superexchange among the four Cu 2+ ions (effected through the intervening oxygen ions in the clusters of (CuO) 4). This may be interpreted as the presence of Pr helps in breaking bonds and killing the superconductivity.