Why do new parties continue emerging and attracting votes in new democracies? Does the duration of the democratic regime facilitate party system stabilization? With original data on legislative elections in fifteen East European countries (1990–2004), this article shows that new party entry is more likely when the cost of entry is low, the benefit of office is high and the perceived level of electoral viability is high. Support for new parties is influenced by the extent of disappointment with existing parties. Further, while the number of new parties decreases gradually as democracies age, the support for new entrants follows no clear unidirectional pattern across time.