This article considers the construct of fluency in second language assessment and how it might be informed by research in applied linguistics. It briefly describes the way fluency is conceptualized in four language tests, as embodied in their respective assessment criteria, to show where the field is at present. The article then takes into account recent insights from applied linguistics, and from the fields of psycholinguistics, discourse analysis, and sociolinguistics. The article questions the current conceptualization of fluency in language testing, in which it is defined as a concept that should be sought in the ear of the beholder, and where disfluency is only seen as a deficit. Future research should focus on finding ways to ensure that the measures used in testing reflect the ability to talk fluently and efficiently, rather than measures that only reflect listeners' impressions about such ability, and to show that these can be marked appropriately and reliably.