Urea Indole Medium is recommended for differentiation of micro-organisms especially Enterobacteriaceae on the basis of their ability to hydrolyze urea and indole production. This medium is very useful in the identification of Proteus species from Salmonella and Shigella species. L- Trypytophan is an essential amino acid and is converted to skatole and indole, which is detected by the addition of Kovacs Reagent (R008). Sodium chloride maintains the osmotic balance. The phosphates helps in the buffering of the medium. Microorganisms that possess the enzyme urease hydrolyse urea , releasing ammonia, which is detected by the pH indicator phenol red . The alkalinility so developed imparts pink colour to the medium. Proteus species show positive urease reaction.