McCoy’s 5A medium, as modified by Iwakata and Grace, is identical to RPMI 1629. Originally in 1959, McCoy and his colleagues described the amino acid requirements for the in vitro culturing of Novikoff Hepatoma cells. Basal Medium 5A was modified to create what is known as McCoy’s 5A Medium for these investigations. Hsu and Kellogg further demonstrated the use of this medium to support the growth of primary cultures derived from normal bone marrow, testes, mouse kidney, skin, gingiva, rat embryo and other tissues. MP’s medium is additionally suited for the propagation of leukocytes, biopsy tissues and the most demanding primary and continuous cell types. It is also available as modified by Park and Terasaki. The Park and Terasaki Modification (PT) differs from the Iwakata and Grace Modication (IG) in that PT contains slightly modified levels of L-glutamic acid, glycine, L-hydroxyproline, L-proline, L-serine, L-threonine, L-tryptophan, and L-valine. The PT modification also contains the additions of penicillin, dihydrostreptomycin sulfate, gentamycin, fetal bovine serum and HEPES.