The introduction of starters represents one of the distinct advances made in the field of dairying. Altho starters have been widely used their careful study has been very much neglected and the men who handle them extensively are often unable to explain the results obtained. The increasing use that is being made of starters in the manufacture of butter, various types of cheese, and fermented milk drinks makes it essential that they be studied with the idea of securing information regarding the reasons for the variations that occur in the quality. The present paper gives the results secured in a study of the volatile acid production of starters and of cultures of the bacteria isolated from them.