Expertise seeking is the activity of selecting people as sources for consultation about an information need. This review of 72 expertise-seeking papers shows that across a range of tasks and contexts people, in particular work-group colleagues and other strong ties, are among the most frequently used sources. Studies repeatedly show the influence of the social network – of friendships and personal dislikes – on the expertise-seeking network of organisations. In addition, people are no less prominent than documentary sources, in work contexts as well as daily-life contexts. The relative influence of source quality and source accessibility on source selection varies across studies. Overall, expertise seekers appear to aim for sufficient quality, composed of reliability and relevance, while also attending to accessibility, composed of access to the source and access to the source information. Earlier claims that seekers disregard quality to minimise effort receive little support. Source selection is also affected by task-related, seeker-related, and contextual factors. For example, task complexity has been found to increase the use of information sources whereas task importance has been found to amplify the influence of quality on source selection. Finally, the reviewed studies identify a number of barriers to expertise seeking.