EU antitrust investigations involve a sequence of events which affect the investigated firm's market value. We model these relationships and estimate their impact on firms' share prices. On average, a surprise inspection reduces a firm's share price by 2.89%, an infringement decision reduces it by 3.57%. The Court judgments do not have a statistically significant effect. Overall, we find that the total effect of the antitrust action ranges from −3.03% to −4.55% of a firm's market value. Fines account for no more than 8.9% of this loss, and we conjecture that most of the loss is due to the cessation of illegal activities.