Given that preprint literature does not undergo the same scrutiny as peer-reviewed literature, are conference proceedings, and in particular, AMS conference proceedings cited in peer-reviewed literature? What is the value of this type of literature and should it be preserved? Has the nature of conference literature changed? Do different user constituencies view the value of this literature differently? We examined the AMS journals for the period 1991-2006, in five-year intervals, looking at the frequency with which conference and other types of literature are cited. We offer some observations and questions and invite opinion and discussion from ASLI members and their preprint users.