What conditions facilitate party system collapse, the farthest-reaching variant of party system change? How does collapse occur? Numerous studies of lesser types of party system change exist, but studies of party system collapse are rare. This study draws on the existing literature and the cases of party system collapse in Venezuela (1988–2000) and Peru (1985–95) to advance some answers to the important questions about the phenomenon. The study posits three conditions that predispose political party systems to collapse: the presence of an acute or sustained crisis that questions the ability of system-sustaining political parties to govern; extremely low or extremely high levels of party system institutionalization; and the emergence of an anti-establishment figure with the desire and personal authority to generate a viable alternative to the established party system. The study also posits a three-election sequential process during which collapse takes place.