Cultures of the family Halobacteriaceae belonging to the species Halobacterium halobium, H. cutirubrum, H. vallismortis and Halococcus morrhuae were shown to be capable of assimilating 14C-succinate. Halobacterium salinarium lacked this ability. The transport systems of C4-dicarboxylates differed in Halobacterium halobium 996 and H. vallismortis 1398, on the one hand, and Halococcus morrhuae 1235, on the other. The differences involve the kinetic parameters and stereospecificity of transport systems, the ability to take up different labelled C4-dicarboxylates, the pH-dependence of transport, and the action of CCCP, a protonophorous uncoupling agent. Halobacteria are capable of labelled succinate uptake at a lower NaCl content in the incubation medium than it is necessary for their growth. The optimal temperature for 14C-succinate uptake by halobacteria is higher than the optimal temperature of their growth. For all of the studied cultures, the transport system of dicarboxylate was shown to differ from that of E. coli common for C4-dicarboxylates and aspartate.