Hyaluronan biology is being recognized as an important regulator of cancer progression. Paradoxically, both hyaluronan (HA) and hyaluronidases, the enzymes that eliminate HA, have also been correlated with cancer progression. Hyaluronan, a long-chain polymer of the extracellular matrix, opens up tissue spaces through which cancer cells move and metastasize. It also confers motility upon cells through interactions of cell-surface HA with the cytoskeleton. Embryonic cells in the process of movement and proliferation use the same strategy. It is an example of how cancer cells have commandeered normal cellular processes for their own survival and spread. There are also parallels between cancer and wound healing, cancer occasionally being defined as a wound that does not heal. The growing body of literature regarding this topic has recently progressed from describing the association of hyaluronan and hyaluronidase expression associated with different cancers, to understanding the mechanisms that drive tumor cell activation, proliferation, drug resistance, etc. No one source, however, discusses hyaluronan synthesis and catabolism, as well as the factors that regulate the balance. This book will offer a comprehensive summary and cutting-edge insight into Hyaluronan biology, the role of the HA receptors, the hyaluronidase enzymes that degrade HA, as well as HA synthesis enzymes and their relationship to cancer.