This practice note discusses the due diligence process in the context of a follow-on offering (i.e., generally, an offering that occurs after an issuer’s initial public offering (IPO)). The due diligence process for a follow-on offering is very similar to the process for an IPO. Underwriters conduct a due diligence investigation in order to establish a “due diligence defense” under Section 11 (15 U.S.C. §77k) and Section 12(a)(2) (15 U.S.C. §77l) of the Securities Act of 1933, as amended (Securities Act). The process typically involves legal due diligence, which requires a detailed review of a variety of corporate documents, contracts, and other materials of the issuer, as well as business due diligence, which typically involves interviews of management and key employees of the issuer, and accounting due diligence, which involves interviews with the issuer’s accountants.