This thesis emphasizes the role of political risk in international business by analyzing the impact of political events on the valuation of firms. The guiding question is how governments interfere with the business interests of firms located in their own country as well as with the business interests of firms from other nations, as a consequence of the application of international sanctions. Therefore, the focus is on multi-country and multi-sector effects due to the occurrence of specific sanction events. The empirical methodology is the event-study approach, which analyzes stock market reactions to new information. The research objective is to detect abnormal stock returns across multiple markets and sectors, as a consequence of events related to the imposition of or threat of international sanctions. The empirical model of this thesis differentiates between risk-effects for firms located in the sender country (i.e., the origin of sanctions), for firms located in or specifically related to target countries (i.e., the receiver of sanctions) and firms located in third countries (i.e., countries not directly involved). There are three different cases analyzed: E.U. Economic Sanctions against African countries (2002-2005), the U.S. Steel Tariff (2002) and the Iran Sanctions Act (2007). The cases represent sanctions applied on the nationwide, sector- and firm-specific level. The event studies provide empirical evidence for the existence of political risk-effects due to sector-specific sanctions. Risk-effects are detected for firms in target countries and for firms in the sender country itself. The applied political risk framework describes how political risk affects multinational firm value and explains that it varies among firms. The impact of political risk on a firm's value depends on the risk exposure of a firm's individual business interests to it. This contributes a new perspective on political risk that emphasizes multinational and multi-sectoral effects and underlines that a specific political risk can be relevant for a variety of different international business interests. (author's abstract)