Magnetic susceptibilities of GdC2, DyC2, and their solid solutions (GdxDy1−xC2; x=0.20, 0.42, 0.51, 0.62, 0.82) have been measured from 4.2 K to room temperature. The dicarbides, DyC2 and GdC2, exhibit antiferromagnetic ordering at 61 and 42 K, respectively. The solid solutions, GdxDy1−xC2, show two cusps on the χ-vs-T curves at TN1 and TN2 suggesting successive antiferromagnetic ordering of spins of the component metal ions. The values of TN1 and TN2 of the solid solutions have been plotted as a function of the average value of the de Gennes factor [?= (g−1)2J (J+1)]. With increasing Gd ion concentration the values of TN1 decrease linearly, whereas the values of TN2 increase. TN1 and TN2 exhibit similar variations with ?. The results have been discussed in the light of the RKKY theory.