This article investigates the value of ethnographic re-studies, and some of the theoretical and methodological issues that carrying out a re-study can generate. It is argued that the disputes that arose around some classic examples in anthropology and community studies are particularly illuminating. For example, Mead's work on Samoa and Redfield's study of Tepoztlán, and the re-studies of these, generated considerable discussion, and this still offers lessons for today. Three key functions of re-studies are discussed: replication, mapping change, and producing a fuller portrait of a community or institution. Also explored is the role of the personal characteristics and the theoretical orientations of researchers. It is concluded that re-studies reveal threats to validity that are present in all social research. At the same time, there is a danger that the discrepancies in findings between study and re-study will be exaggerated, indeed that the methodological problems involved will be mistakenly treated as representing a logical impasse.