 Ancient Greeks and Romans confronted the need to select and store information, with a view to subsequent retrieval. A number of textual formats were used to store, organise and permit retrieval of various sorts of information. This chapter argues that certain types of texts (including doxographies, or collections of opinions) provided an archival function for studying topics and issues in scientific fields such as natural philosophy and medicine, allowing the accumulation, organisation, retrieval and use of data and ideas. Considering the functions of these and related texts can shape our understanding of ancient Greek and Roman scholarly and investigative methods. A crucial feature of doxographical texts is their archiving of already-produced opinions about nature, rather than ‘raw data'. In some cases, as Aristotle and others noted, we have to work with opinions because of a lack of data. One aim of doxography, as an ancient archiving text, is to allow the philosophical and scientific work of hypothesizing and explaining to proceed. It is perhaps only in later periods that ancient doxography becomes a repository of what had been selected to endure as archives of past philosophical and scientific enterprises, rather than as material to be mined for active scientific projects.