The inhibitory effects of sodium dehydroacetate (DHA-Na) and sodium sorbate (SA-Na), added at 0.02-0.10% level, on acid production, proteolysis and aroma production by five strains of lactic acid bacteria, were investigated in skimmilk and some other milk media. Acid production of some lactobacilli including L. bulgaricus when incubated at 37°C for 24 and 48hr, was inhibited remarkably by the addition of 0.10% DHA-Na to skimmilk media. The similar inhibition occurred with 0.02-0.10% level of SA-Na, especially in the case of S. lactis. Proteolysis by the cultures when incubated for two days was retarded significantly by the addition of the preservatives at 0.08-0.10% level, whereas at the same level of preservatives the inhibition of the cultures when incubated for four days was not so significant. The presence of 0.02% level of preservatives had little effect on proteolysis. On the aroma (diacetyl and acetoin) production by S. lactis and some lactobacilli incubated for two and four days, some inhibitory effect took place when 0.04% DHA-Na or SA-Na was present, and it became nearly complete at the 0.08-0.10% level. Conclusively, some critical problems concerning reasonability of the addition of preservatives to commercial fermented milk beverage were discussed.