Brain Heart Infusion Broth (BHI) is an enriched non-selective medium intended for the cultivation of most anaerobic bacteria and other fastidious microorganisms. This medium is used in the inoculum preparation for antimicrobial susceptibility testing, is especially useful as a base for blood cultures and is also used in the broth-disc antimicrobial test procedure as described by Wilkins and Theil. BHI is an enriched non-selective broth medium that is useful in the cultivating of fastidious and non-fastidious microorganisms. This medium will also support the growth of aerobic microorganisms from a variety of clinical and non-clinical specimens. The basal medium is infusion from brains and beef heart and supplemented with vitamin K1 and hemin as growth factors for most anaerobes. This medium is prepared, dispensed, stored and packaged under oxygen-free conditions to prevent the formation of oxidized products prior to use. This medium contains resazurin as a redox indicator which turns pink upon significant oxygen exposure.