The reverse micelle system of sodium di-2-ethylhexyl phosphate was used to extract aminoglycoside antibiotics, neomycin and gentamicin. The aminoglycosides can be efficiently extracted into a reverse micelle solution, and the antibiotics extracted into the micelle phase can readily be recovered back to a divalent cation aqueous solution, such as Ca 2+ . The transfer efficiency, % E , is heavily dependent on pH and salt concentration in the aqueous feed solution. % E decreases drastically with pH in the pH range 8·5–11, and declines with increasing (NH 4 ) 2 SO 4 concentration. A simple transfer mechanism was proposed which suggests that the antibiotic molecules were extracted into the inner water cores of reverse micelles through attractive electrostatic interaction during forward transfer. In backward transfer, the antibiotics loaded in the micelle phase are released back to an aqueous phase through breaking up of the reverse micelles by using divalent cation solutions. The model is supported by the results of dynamic light scattering and infra-red spectroscopy study.