Facilitated membrane extraction (FME) has been examined for the continuous isolation of lactic acid from its dilute solutions. The technique is intended for continuous fermentation technology, with the pH of a broth regulated by extraction of the acid. Standard dialysis membranes and a conventional diffusion dialyzer were the equipment used for carrying out the separation. By FME, slow diffusional transport across a membrane is accelerated by the neutralization of an acid in the receiving side of a dialyzer. By using this technique the fluxes of lactic acid were found to be 0.7-1.3 mol.m(-2)h(-1) (pH 11.7-12.8) against 0.013-0.015 mol.m(-2).h(-1) reported for conventional diffusion dialysis (the same feed, C-acid = 0.01 mol.dm(-3)). The accumulation of lactate in a permeate established experimentally was 0.5-0.6 mol.dm(-3). The concentration of lactic acid left in a feed after extraction was 10(-3)-10(-4) mol.dm(-3). FME integrated with electrodialysis seems to offer an effective separation system for continuous fermentation technology.