The truth, the TV show The X-Files told us, is out there. Millions of people worldwide seem to agree, disbelieving official accounts of important social and political events. In the United States, for example, scholars have noted a steady increase in the number of poll respondents who believe that Lee Harvey Oswald did not act alone in killing John F. Kennedy (Goertzel, 1994; McHoskey, 1995). In the wake of 9/11, commentators highlighted the proliferation of conspiracy theories about the event (e.g. Goldberg, 2004), with polls suggesting that more than a quarter of respondents believe the US government knew in advance (Zogby International, 2004), participated in, or took no action to stop the attacks (Hargrove & Stempel, 2006).But conspiracy theories are not a uniquely American phenomenon: in a poll of seven predominantly Muslim countries, Gentzkow and Shapiro (2004) reported that almost four fifths of respondents did not believe the 9/11 attacks were carried out by Arabs, believing instead that it was the work of the US or Israeli governments (for other conspiracy theories in the Middle East, see Zonis & Joseph, 1994). In Britain, the BBCs documentary series The Conspiracy Files has examined a range of theories in current circulation, including those about the deaths of Princess Diana and UN weapons inspector David Kelly, the bombing of PanAm Flight 103, and the London bombings of 7 July 2005.Given such widespread belief in conspiracy theories across the globe, it comes as something of a surprise to learn that there remains a dearth of empirical research on the topic (Abalakina-Paap et al., 1999). Part of the problem may be that academics have traditionally not engaged with conspiracy theories for fear of being branded as conspiracy theorists themselves. Until recently, it was not uncommon to find accounts of possible or real conspiracies prefaced by disclaimers of the kind that Ramsay (1990) notes: In intellectually respectable company, it is necessary to preface any reference to... conspiracies with the disclaimer that the speaker doesnt believe in the conspiracy theory of history (or politics). A related problem is in distinguishing between a conspiracy theory and an awareness of genuine political conspiracies. A broad definition of the former was provided in Hofstadters (1966) seminal essay, The paranoid style in American politics, where a conspiracy theory was described as a belief in the existence of a vast, insidious, preternaturally effective international conspiratorial network designed to perpetrate acts of the most fiendish character (p.14; for extended discussions, see Bale, 2007; Sunstein & Vermeule, 2009). That such beliefs are relatively widespread suggests that they fulfil certain social functions or psychological needs; given this role, conspiracy theories are deserving of the same academic study as other religious, political or social beliefs (Bale, 2007).The remainder of this article discusses both early work in sociology and cultural studies on the causes of conspiracy theorising, and emerging psychological research focused on the individual difference antecedents of conspiracy theories. We conclude with reasons why further research on conspiracy theories is important, both in terms of academic research and sociopolitical practice.Early sociological work Hofstadters (1966) essay on the paranoid