Implicit bias reduction has become an increasingly popular feature of so-called 'diversity training' in both public and private organizations. It remains popular, despite a lack of robust evidence suggesting that it is possible to accomplish lasting changes to individual implicit bias. In addition, previous research relies almost entirely on laboratory experiments; almost nothing is known about the scope of these findings. The present study aims to engage theoretically and empirically in this debate. An implicit bias reduction intervention developed by psychologist Patricia Devine will be tested and approached from a sociological perspective. The study is based on an experiment setting with social workers at 13 Swedish social assistance units. Beyond testing the scope of this particular intervention, the study highlights some of the methodological problems that come with the unrealistic standards of exact replication within the social sciences. The results show that the intervention increased the participants' awareness of prejudice and implicit bias, but it did not reduce the participants' implicit biases. The scientific and social policy consequences of these findings are discussed.