This volume reviews a series of different publications dealing with orotic acid. Orotic acid was isolated from cow's milk 75 years ago by Biscaro and Belloni in Italy. Fifty years later again Italian scientists described the growth-promoting activity of orotic acid in vitamin B -deficient animals. 12 Orotic acid is the precursor of pyrimidine nucleotides which are involved in many biochemical reactions: UTP and CTP, as substrates for RNA polymerase, and UDP sugars, as substrates for carbohydrate containing macromolecules, e.g. glycogen, glycoproteins and glycolipids. The biosynthesis of these...