[en] Magnetization and magnetoresistance (MR) measurements were performed on pyrochlores Gd₂Mo₂O₇ and Gd₂(Mo_0.6V_0.4)₂O₇. It was shown that both compounds are ferromagnets below T_C=80 K with the same alignment of magnetic moments of 4f and 4d ions. The substitution of Mo ions by V leads to the increase of the resistivity without changes in the magnetic state. Gd₂Mo₂O₇ exhibits a large negative magnetoresistance ratio, especially in the low-magnetic-field regime, which increases strongly with decreasing temperature. In Gd₂(Mo_0.6V_0.4)₂O₇ below T_C the magnetoresistance ratio changes from negative to positive with decreasing temperature. These data indicate that the mechanism of the magnetoresistance effect in the molybdates differs markedly from that for manganites studied in detail with perovskite and pyrochlore structures. (author)