The private exchange of prices by competitors has long been a source of anticompetitive concern. Based on claims of possible procompetitive effects, the Supreme Court decided that antitrust challenges to these exchanges should be evaluated under the rule of reason. In reviewing the jurisprudence applying the rule of reason approach to horizontal price exchanges, we find it suspect as it is long on claims of procompetitive benefits but short on economic theory and evidence substantiating those claims. To fill this gap, this article injects economic reasoning into the judicial discussion. While our analysis identifies several reasons for these exchanges to have anticompetitive effects, none of the claims of procompetitive effects survive close scrutiny. The case for applying the rule of reason to horizontal price exchanges is based on factually incorrect claims of economic effects. Though the evidence supports per se condemnation, courts are unlikely to treat horizontal price exchanges as per se illegal. We propose the quick look rule as a compromise.