During the last few years evidence has been presented which shows that starters are not pure cultures of S. lacticus. Hammer and Bailey, Storch and Boekhout and Ott de Vries have found that starters contain organisms other than S. lactic us that are important from the standpoint of volatile acid and odor and flavor development. More recently Hammer4has secured data that indicate the source of the volatile acidity produced by the organisms associated with S. lacticus and has also shown that starters do not contain pure lactic acid as they would be expected to if they were pure cultures of S. lacticus. The percent of the total acidity represented by volatile acid at various times during the period of rapid acid development is quite different with starters than it is with pure cultures of S. lactictus, and this difference offers further proof that starters are not pure cultures; data on this point are presented herewith . .