Haemophilus influenzae is differentiated from other Haemophilus species primarily by its growth requirements for both hemin (called factor X in the old literature) and nicotinamide adenine dinucleotide (NAD or factor V). H. influenzae strains normally grow well in rich media such as brain heart infusion (BHI), suitably supplemented with hemin and NAD (sBHI), and on sBHI or chocolate agar plates. Many isolates classified as H. influenzae differ in their other nutritional requirements, for a purine and for specific amino acids (1,2). Thus, although a number of defined media have been described, their use often leads to frustration. The medium MMB, described by Klein and Luginbuhl (2), is simplest to prepare; when supplemented with a small amount of casamino acids it reproducibly gives good growth.