An investigation of the possibility of developing a differential medium for isolation of soil bacteria in the family Rhizobiaceaa was conducted. Although the observation was made that pure cultures of I Rhizobium were able to grow on the rose bengal agar of Smith and Dawson, bacteria in the family Rhizobiaceae did not develop when soil was used as the inoculum, The predominate groups of bacteria which developed on this medium from soil were in the families Achromobacteriaceas and Pseudomonadaceae, Organisms chosen to represent the groups of bacteria in the families Achromobacteriaceae and Pseudomonadaceae were identified tentatively in the genera Flavobactgerium and Pseudomonas, respectively. / Master of Science