A discussion of exceptions commonly included in negative assurance letters (10b-5 letters) delivered by counsel in securities offerings. This Practice Note explains the role of the 10b-5 letter in supporting the underwriters' due diligence defense and examines common carve-outs for expertized disclosure. In addition, this Practice Note discusses carve-outs relating to statistical data and for disclosure covered by special counsel and for a trustee's statement of eligibility on Form T-1.