Acid fast, pathogenic and non-pathogenic bacteria, including human tubercle bacilli, bovine tubercle bacilli, B. C. G., and timothy bacillus were grown on a sterol free medium. Methods for the extraction and treatment of the bacteria are described. Sterol was present in the extracts of the bacterial bodies tested with Burchard-Liebermann, Sal-kowski, and other color reactions. In the culture medium both before and after the growth of the bacteria, no sterol was demonstrable.