This article looks at the concept “known item search” (KIS) and considers it in relation to library practices. The author critically examines previous research on KIS and argues that the concept is important because it is categorically different from “subject search” and because it is assumed in processes such as bibliographic verification and descriptive cataloging. The article further discusses which kinds of metadata best serve KIS and argues that the traditional distinction between descriptive cataloging and subject cataloging is a fruitful point of departure for describing the metadata needed for respectively KIS and subject searches.