A simplified method of isolating monophasic vars. from diphasic Salmonella cultures, incorporating the principles of Gard (Z. Hyg., 120 59), Edwards and Bruner (Univ. Kentucky Circ. 54), and Wilcox (Army Med. Center, Memo., Feb., 1944), by the use of a "U" tube, has been employed with satisfactory re- sults. The semisolid agar used is Edwards and Bruner''s modification of that of Jordan, Caldwell, and Reiter (Jour. Bact. 27: 165). The reaction of the medium is adjusted to pH 7.4. 4 ml. of the medium is dispensed into 12 mm. X 100 mm. tubes and autoclaved at 15 1b. pressure for 15 min. For routine use, a test tube of semisolid agar medium is melted and cooled to 45-50[degree] C. A small loopful (not over 2 mm. in diam.) of agglutinating serum (undiluted) of the phase to be suppressed is added to the test tube containing the melted, cooled agar medium, and is thoroughly mixed; then the whole is aseptically transferred to the "U" tube by means, of a sterile 5-ml. pipette." The medium plus the serum is allowed to solidify. Inoculation of the medium in one end of the tube is accomplished by barely penetrating the surface of the medium. The tube is incubated at 37[degree] C until diffuse growth reached the surface of the agar in the other end of the "U" tube. Growth is aseptically removed from that end to a tube of infusion broth, and the resultant growth is used as "H" antigen for demonstration of the phase under study. Results in many cases will be so much more definite by using this procedure that the additional work is justified. The "U" tube can also be advantageously used, without agglutinating sera, to enhance the motility of a monophasic culture, which may then be used for anti-serum production.