This article examines three differences between the party systems of the advanced industrial democracies and party systems of less developed countries, particularly in terms of the level of institutionalization. The overarching argument is that the party systems of less developed countries are less institutionalized. More specifically, we first show that most democracies and semidemocracies in less developed countries have much higher electoral volatility and less electoral stability than the advanced industrial democracies. Second, much of the literature on voters, parties and party systems assumes the context of institutionalized party systems with strong party roots in society and further presupposes that party competition is based on programmatic or ideological linkages between voters and parties. However, in the party systems of most democracies and semidemocracies in less developed countries, these programmatic or ideological linkages are substantially weaker. Third, linkages between voters and candidates are more personalistic in the less institutionalized party systems of the democracies and semidemocracies.