Do by-elections have the same characteristics and follow the same tendencies that general elections do? We propose an analysis of the turnout and the performance of minor parties during Quebec’s by-elections since 1970. We also examine the performance of by-election elected incumbents in subsequent general elections. Finally, we verify if by-elections constitute, as many suggest, referendums on the government. In short, we try to determine the dynamics specific to by-elections as well as their importance in Quebec’s political life.