Hole and electron mobilities have been measured in ternary solid solutions containing an electron acceptor, 4H-1,1-dioxo-4-dicyanomethylidene-2-p-tolyl-6-phenylthiopyran, and an electron donor, tri-p-tolylamine, in a polyester host. The results are discussed by a model based on disorder, due to Bässler and coworkers. The key result of this study is that the presence of the donor has no effect on electron transport, nor does the presence of the acceptor have any effect on hole transport. The interpretation of the experimental results leads to the conclusion that the electron and hole manifolds are independent and are not influenced by the presence of the transport states of the oppositely charged carriers.