The exopolysaccharide (EPS) production and growth characteristics of Lactobacillus casei CRL 87 under pH control were studied. Maximum polymer synthesis (488 mg/l) and cell viability (2.4x10(10) cfu/ml) occurred when L. casei was cultured at a constant pH of 6.0 and 30 degrees C for 24 h. However, the optimum specific EPS production (3.9x10(-5) g EPS/g cell dry weight) and EPS yield (4.3%) were found at a pH of 4.0.