This practice note describes the antitrust risk of competitors exchanging competitively sensitive information. Information exchange is a horizontal restraint that may violate Section 1 of the Sherman Act. While some information exchanges can be procompetitive or at least consistent with normal interdependent commercial behavior, others can lead to anticompetitive effects. For this reason, courts and authorities analyze exchanges of competitively sensitive information under the rule of reason. Additionally, information exchanges may serve as evidence of per se illegal conduct. This practice note describes competitively sensitive information, a rule of reason analysis of information exchanges, information exchange that may be evidence of per se illegal conduct, and two contexts in which competitors often exchange competitively sensitive information (premerger and joint ventures). Throughout, the note lays out tips for counsel to spot and manage the risks of information sharing.