The precipitation of two transport proteins, cytochrome c and hemoglobin, was carried out by using di-(2-ethylhexyl) sulfosuccinate, known as aerosol-OT (AOT), as a precipitating agent. The percent precipitation was 100% when the molar ratio between AOT and the targeted protein was 11 for cytochrome c and 30 for hemoglobin. By using acetone as a polar solvent, the maximum recovery obtained was 98% for cytochrome c and 40% for hemoglobin. The surfactant contamination in the recovered product was below the detection limit. The required usage of surfactant-to purify 1 mole of targeted protein was many orders of magnitude smaller than that required for a reverse micellar extraction when using AOT. Advantages of the suggested precipitation method over the reverse micellar extraction method for protein purification are discussed.