Studies in Chinese hamster ovary cells demonstrate the presence of an anion exchanger, which has some of the properties of the band 3 transporter in erythrocytes. 1) Extracellular chloride is a competitive inhibitor of sulfate influx and stimulates sulfate efflux, suggesting that the mechanism of uptake is SO42-/Cl- exchange. 2) The anion exchange inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid inhibits sulfate uptake in a dose-dependent manner. Half-maximal inhibition is achieved at 0.06 μM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. 3) Low extracellular pH markedly stimulates sulfate uptake. A 6-fold decrease in the apparent K(m) is observed at pH(out) 5.5 as compared to pH(out) 7.5. However, studies carried out over a broad range of extracellular SO42- concentrations indicate the presence of three components of this transport activity in Chinese hamster ovary cells: two high affinity low capacity systems, one in the range 0.5 μM < [SO22-](out) < 50 μM and one in the range 50 μM < [SO42-](out) < 150 μM, and a low affinity, high capacity system (at [SO42-](out) > 150 μM). These properties have not been previously reported for the erythroid band 3 transporter. The availability of mutants deficient in these activities has enabled us to carry out studies which suggest that the high affinity systems are functionally independent of the low affinity system, but that all systems are dependent on the same anion exchange protein. Studies in a mutant which lacks all components of the transport activity indicates that the anion exchanger may be instrumental in the regulation of the intracellular pH in Chinese hamster ovary cells.