http://implicit.harvard.edu/ was created to provide experience with the Implicit Association Test (IAT), a procedure designed to measure social knowledge that may operate outside awareness or control. Significant by-products of the website's existence are large datasets contributed to by the site's many visitors. This article summarises data from more than 2.5 million completed IATs and self-reports across 17 topics obtained between July 2000 and May 2006. In addition to reinforcing several published findings with a heterogeneous sample, the data help to establish that: (a) implicit preferences and stereotypes are pervasive across demographic groups and topics, (b) as with self-report, there is substantial inter-individual variability in implicit attitudes and stereotypes, (c) variations in gender, ethnicity, age, and political orientation predict variation in implicit and explicit measures, and (d) implicit and explicit attitudes and stereotypes are related, but distinct.