Originally developed by Mueller and Hinton only for the isolation of pathogenic Neisseria, Mueller Hinton agar medium is now considered as a standard culture medium for routine susceptibility testing of non-fastidious microorganisms to antibiotics. Bauer and Kirby have recommended this medium for performing antibiotic susceptibility tests using a single disc of high concentration. It is also recommended by FDA, WHO and CLSI for testing the most commonly encountered aerobic and facultative anaerobic bacteria in food and clinical material. The medium displays good batch-to-batch reproducibility, is low in sulfonamide, trimethoprim and tetracycline inhibitors and allows satisfactory growth of most of the non-fastidious pathogens. This medium can also be used as Mueller Hinton blood agar medium that is basically MHA supplemented with blood for the antimicrobial disk diffusion testing of Streptococcus spp., including Streptococcus pnuemoniae.