This chapter discusses the Implicit Association Test (IAT) and its variants as novel measures for implicit language attitudes. The IAT is a reaction time-based categorisation task that measures automatic associations between a target and attribute concept. In the case of language attitudes, this comes down to measuring whether people automatically associate a language (variety) or linguistic feature with positive/negative valence or with specific social attributes of the speaker. The method originates in social psychology, where it has been used to study a wide variety of topics (e.g. racial bias, self-esteem), and has recently been introduced to linguistics to study the social meaning of language variation. This chapter discusses the merits and potential disadvantages of using the IAT paradigm for such linguistic purposes. In addition, the chapter gives a practical introduction to setting up a study using the IAT paradigm and explains how to analyse the reaction time data harvested in the experiment and interpret the results. The main points of the chapter are illustrated with a case study that uses the P-IAT to measure associations with Standard Belgian Dutch as well as two regional varieties of Belgian Dutch.