Cobalt(II) has been extracted by 50% (v/v) TBP solution in benzene from HC1, HBr, and LiC1 solutions containing water miscible alcohols and nonbesic and basic aprotic solvents. All solvents used caused the distribution ratio of Co(II) to increase due to diminished water activity and shifts in equilibria of cobalt(II) complexes in solutions. Hexamethylphosphor-triamide (HMPTA) has been found to behave exceptionally in that it extracted Co(II) from LiC1 solutions into neat benzene and in the presence of TBP induced a weak synergism caused by extraction of at least two mixed solvates.