This paper examines residents' attitudes to a major non-sport-related mega event, the 2010 Shanghai Expo. Resident attitudes research can ascertain how best to accommodate host community views, a key issue in developing sustainable tourism strategies. The paper breaks new ground by examining attitudes both before and during the event, revealing considerable fluidity in attitudes, and it examines residents' attitudes in China, reflecting the importance of non-western cultural and political systems on attitude development. The paper contributes to longitudinal research, an area where little research is available. Two studies were conducted before and during the 2010 Shanghai World Expo using the same survey instrument. It is based on a representative sample of residents of Shanghai who were asked about their attitudes to Expo 2010. Results indicate that residents on the whole strongly supported (77.9%) or supported (12.7%) the event with all the average scores of the attitude items higher than 5 (on a 1-7 scale). Some negative impacts were identified such as increased prices, traffic problems, crowding and congestion. Residents were classified into three groups in the pre-event survey (whole embracer, ambivalent embracer and neutralist), according to their level of support, and two groups for the survey during the event.