Abstract. With the recent acceleration of the integration process of the European Union there has been a rise in political parties expressing either scepticism or outright criticism of the nature of the integration process. Using a four–fold differentiation between single issue, protest, established parties and factions within parties, the first part of the article presents an overview of Euroscepticism within EU member states and Norway. This reveals the diversity of sources of Euroscepticism both in ideology and in the types of parties that are Eurosceptical but with a preponderance of protest parties taking Eurosceptical positions. The second part of the article is an attempt to map Euroscepticism in West European party systems through a consideration of ideology and party position in the party system. The conclusions are that Euroscepticism is mainly limited to parties on the periphery of their party system and is often there used as an issue that differentiates those parties from the more established parties which are only likely to express Euroscepticism through factions. Party based Euroscepticism is therefore both largely dependent on domestic contextual factors and a useful issue to map emergent domestic political constellations.