Regeneration of microcapsules was carried out by stripping the extracted propionic acid with distilled water and aqueous NaOH solution based on data obtained for a liquid-liquid system. Concerning the stripping behavior with distilled water, the stripping reactions can be successfully expressed as the reverse formula of the extraction reactions. The stripping ratio was found to be a function of the concentrations of the extracted propionic acid in organic solution and the propionic acid in aqueous solution at equilibrium. For aqueous NaOH solution, on the other hand, the stripping could be expressed by the following stoichiometric reaction in the organic solution in both the liquid-liquid and the microcapsule systems. (HA) B (HA)n-1 + nNaOH = B + nNaA + nH2O Perfect stripping was achieved when the molar ratio of NaOH to propionic acid was larger than unity. The microcapsule extraction system showed the same extraction capacity after repetitive extraction and stripping of propionic acid.