Proportional Representation on Trial examines the 1999 election in New Zealand and its aftermath. The last electoral contest of the twentieth century resulted in a complete change of government. In 1999 Labour returned to power as the main party in a coalition minority government. Proportional representation in the form of MMP made the difference. The fourth in a series of election studies, Proportional Representation on Trial traces the evolution of public attitudes to MMP, presents a comprehensive assessment of the effects of proportional representation, and discusses the experiment of the two citizen-initiated referendums.