An underwriting arrangement in which an underwriter agrees to purchase all of the securities being offered for resale to the public, thereby, in theory, assuming the risk of finding buyers. In practice, this risk is very slight by the time an underwriter becomes legally obligated to purchase the securities from the issuer, as the underwriters will already have 'built a book' of investors who have indicated an interest in buying the securities. See 'All-or-None' and 'Best Efforts Underwriting' for comparison.