Diary researchers use pre-existing or solicited diaries, documents made up of regular dated entries. Such documents are particularly useful for researchers who would like to observe specific phenomena but are unable to do so because they took place before the research started or are intrinsically difficult to observe. Diaries can also provide ways of accessing voices that are often silenced in public discourses such as those of gay men, members of countercultures, or women. Diaries can be used as a source of data in a variety of research designs, including experimental and survey research that use structured diaries to collect specific data from selected groups as well as interpretive, ethnographic research that examines the ways in which diarists narrate their life and experiences. While the entries in diaries may appear to be accurate records of diarists’ observations and reflections, they are shaped by diarists’ interests and by social, cultural, and literary conventions. Furthermore, dated entries may not be written at the specified time and may be subsequently edited by the diarist and others. Researchers can respond to such issues by maximising their control over the ways diaries are used and entries made, for example, by carefully selecting diarists and providing them with detailed instructions on how to complete their diaries. An alternative approach is to focus on the underlying structure of diaries and explore why diarists have chosen to keep diaries as well as how they used existing conventions to narrate their stories.