The 1999 election produced probably the lowest voting turnout of any twentieth-century New Zealand election. Yet it was the second election after a change to proportional representation from a first-past-the-post system, which comparative research indicates should have had the effect of turnout increase. This puzzle is examined using pooled validated data from the 1996 and 1999 New Zealand Election Studies, with particular attention to the effects of partisan dealignment, party mobilization and the short-term effects of New Zealand's first experience of coalition government since the 1930s.