In an ever more globalized financial market, investors are increasingly exposed to regulation and enforcement by multiple jurisdictions with varying rules, including different insider trading regimes. From a European perspective, potential exposure to the U. S. insider trading regime is particularly challenging. Especially for the non-U. S. practitioner, the U. S. insider prohibition is very complex and offers little legal certainty. And this uncertainty is all the more problematic for Europeans because the U. S. insider ban applies extraterritorially. Even more worrying, violations of the U. S. insider trading regime are often met with harsh consequences, ranging from stiff prison sentences to ruinous financial penalties. First, this article broadly outlines the contours of the U. S. insider trading regime as well as the current state of play for insider trading enforcement under U. S. law. Second, it outlines the fearsome (extra-) territorial reach of the U. S. insider trading ban, to allow a better assessment of a European’s potential exposure to the U. S. insider trading regime in different situations. Third, it highlights the main differences between the U. S. and the EU insider trading regulations, to identify the areas in which market participants on both sides of the Atlantic should be particularly cautious.