First discussed are limitations on the reach of Rule 10b-5, a broad antifraud provision of the Federal securities laws. The origins and development of the misappropriation theory and the application of the mail fraud statutes as applied to Section 10 are examined. Basic, Inc. v. Levinson provides the context analyzing the duty of disclosure and the timing of disclosure of merger negotiations, along with the fraud-on-the-market theory of civil liability. The paper notes that the Supreme Court's split in the Carpenter decision indicates that legislative clarification of the definition of insider trader is needed. The ruling also confirms that unauthorized use of confidential business information can constitute fraud under mail and wire fraud statutes. The Court's acceptance of the fraud-on-the-market theory advances the goals of Federal securities law and permits investors to rely on the integrity of the market's pricing mechanisms to establish securities prices. 166 footnotes.