This article discusses the antitrust issues concerning exchanges of competitively sensitive information (CSI) in vertically integrated firms, an area of increasing concern in the US in particular. In-house counsel often face the challenge of ensuring that their organization properly maintains CSI, a challenge that becomes dramatically more complex when the organization is vertically integrated and transacts with third parties who are suppliers or customers on the one hand, and competitors on the other. A broad spectrum of business units within the organization may wish to access CSI to implement strategic business plans designed to increase efficiencies and maximize profit. However, unfettered circulation of CSI within an organization can lead to antitrust problems – a vertical merger that creates the opportunity for exposure to a competitor’s CSI may be found unlawful under Section 7 of the Clayton Act and the actual exchange of such information may be found to violate Section 1 of the Sherman Act or other antitrust laws. The article includes practical advice for in-house counsel to help manage the risks.