[en] The conventional theory of superconducting alloys does not take into account the discrete character of impurities. Experimental data for superfluid ³He in aerogel and for some high-T_c superconductors reveal a significant discrepancy between the observed temperatures, T_c, of their transitions in the superfluid or superconducting states and those predicted theoretically. Here a theoretical scheme is presented for finding corrections to the T_c originating from spatial correlations between impurities. Analysis is limited to the Ginzburg and Landau temperature region. The shift of T_c with respect to the pure material is represented as a series in concentration of the impurities, x. In the first order on x, the conventional mean-field result for lowering T_c is recovered. The contribution of correlations enters the second-order term. It is expressed via the structure factor of the ensemble of impurities. For superfluid ³He in a silica aerogel, the sign of the correction corresponds to an enhancement of the T_c, so that the resulting pair-breaking effect of impurities is weakened. When the correlation radius of the impurities, R, exceeds the coherence length of the superfluid, ${\mathrm{\xi <!--\; ??\; -->}}_0,$ the contribution of correlations to the shift of T_c acquires a factor, $\sim <!--\; ???\; -->{(R/{\mathrm{\xi <!--\; ??\; -->}}_0)}^2,$ and the weakening of the pair-breaking effect becomes appreciable. The presented scheme is applied to the superfluid ³He in aerogel. (paper)