The extraction of lactic acid with Aliquat 336 dissolved in dodecane and decanol was investigated at various experimental conditions. To determine the concentration of extracted anions and undissociated molecules in the organic phase, the experimental results were treated by mass balance equations of lactic acid and hydrogen concentration in both phases. Thus, the ratio between the extracted anions and whole (undissociated) molecules was calculated. This ratio depends strongly on the pH and lactic acid concentration. The overall distribution coefficient rises or decreases with the pH increase in dependence on lactic acid concentration. The obtained linear dependence of the acid molecules concentration in the organic phase on their concentration in the aqueous phase is a strong argument to suppose physical extraction by Aliquat 336.