Chocolate agar (CHOC) or chocolate blood agar (CBA), is a nonselective, enriched growth medium used for isolation of pathogenic bacteria. Chocolate agar is used for growing fastidious respiratory bacteria, such as Haemophilus influenzae and Neisseria meningitidis. In addition, some of these bacteria, most notably H. influenzae, need growth factors such as nicotinamide adenine dinucleotide (factor V or NAD) and hemin (factor X), which are inside red blood cells; thus, a prerequisite to growth for these bacteria is the presence of red blood cell lysates. The heat also inactivates enzymes which could otherwise degrade NAD. Medium contains Proteose peptone is a nitrogen source required for the growth of wide variety of organisms. Dextrose acts a carbon energy source. Disodium phosphate buffers the medium whereas sodium chloride maintains the osmotic equilibrium. Agar is the solidifying agent. Heated sheep blood is added to give the medium its “chocolate” appearance. This medium is prepared, stored and dispensed under oxygen-free conditions to prevent the formation of oxidized products prior to use.