Haziness that spreads from the stab line indicates a positive test for motility. Tubes must be compared to an uninoculated tube to discriminate between faint haziness and motility. A red color development after addition of Kovács reagent indicates indole production. A black precipitate indicates H2S production. Test tubes: (A) uninoculated tube, (B) contains the nonmotile and indole-negative bacterium Klebsiella pneumoniae, (C) contains the motile and indole-positive bacterium Escherichia coli, and (D) contains the motile, indole-negative, and H2S-producing bacterium Proteus mirabilis. (Renee Wilkins, University of Mississippi Medical Center, Jackson, MS)