This chapter reviews published studies of the use of pictorial information. Examining image user studies surfaces several research questions often addressed by this body of work, as well as some frequently encountered problems. These questions and problems organize this survey of the literature. Image user studies were included in two valuable reviews of digital image research and development, published by Christie Stephenson and Corinne Jörgensen in 1999 (Jörgensen, 1999; Stephenson, 1999). This overview considers research since that time, focusing on assessment that was not targeted at a single system or service. While attempting to incorporate some interesting research from the information and educational technology communities, this discussion of image delivery as an aspect of digital library development limits coverage of those important literatures. During the 1980s and early 1990s, digital images were usually approached as a technical problem. At that time in higher education and cultural institutions, projects and publications focused on the mechanics, standards, and labor for creating, describing, storing, and retrieving image files and study continues in those areas. Digital images were a novelty then and user studies were largely confined to "laboratory" environments. User studies for image delivery were moved from the lab to the field by the American Memory User Evaluation, conducted at 44 schools and libraries between 1991 and 1993, and the Museum Educational Site Licensing Project (MESL), which was conducted between 1994 and 1997 at seven museums and seven universities (Stephenson and McClung, 1998a,b; Veccia et al., 1993). Since that time, the perception of digital images has changed from novel to inevitable. Now faculty members say, "They are here to stay" and "They are expected by students and peers" (Farley, 2004). This growth in the popularity of digital images, together with a general increase in assessment of information services, has stimulated an abundance of research since the American Memory and MESL projects. Image user studies have employed the full range of methods found in other digital library assessment. Listing some of the large-scale studies illustrates this:. Museum Educational Site Licensing Project (MESL), 1994-1997, (Stephenson and McClung, 1998a,b)•Scope: Images of artworks produced by seven museums and mounted on separate systems by seven universities.•Methods: Pre-test and post-test surveys and focus groups.•Related work: Follow up study comparing the costs of the MESL distribution method to distribution via 35mm slide libraries (Besser and Yamashita, 1998). The AMICO University Testbed project which informally evaluated use of the AMICO Library image database at sixteen colleges and universities (Art Museum Image Consortium, 1999; Gay and Rieger, 1999). Visual Information-Seeking Oriented Research (VISOR) 1999-2002 (Conniss et al., 2000, 2003)•Scope: Study of picture searching in ten different organizations, including academic, commercial, research, cultural, and governmental settings conducted by researchers at Northumbria University.•Methods: Structured interviews and observations of searches with framework analysis.•Related work: Further testing of the VISOR categories of image use by other researchers at Northumbria1 (Eakins et al., 2004). Visual Image User Study (VIUS), 2001-2003 (Pisciotta et al., 2005)•Scope: Assessment of picture use and needs for digital image delivery across many disciplines (arts, humanities, and environmental sciences) at a large and complex school, Pennsylvania State University.•Methods: Surveys, focus groups, interviews, authentication logs, prototyping, think-aloud protocols, pre-test and post-test surveys.•Related work: The California Digital Library's Image Service Demonstrator Project assessing user requirements for image delivery at the University of California campuses11Only the preliminary reports from these projects were available at the time of this writing.(Farley, 2004). Use of Digital Resources in Humanities and Social Sciences Undergraduate Education (shortened here to UDR), 2003-20051 (Harley, 2004)•Scope: Multi-institutional assessment of the availability and use of all forms of digital resources for undergraduate education in the humanities and social sciences. Included here since the first phase includes substantive information about digital image use.•Methods: Surveys, focus group discussions, interviews, and transaction log analysis. This group of projects has implemented all of the methods listed in Denise Troll Covey's survey of the assessment methods applied at Digital Library Federation (DLF) member institutions. (Covey, 2001). These studies, and the others cited below, have been very difficult to compare, since the conditions, definitions, and metrics vary. Those interested in any of the specific findings mentioned in this article should consult the source so that the result can be understood in its original context. As a body of work, the past decade of image user studies have treated these questions about image delivery:•Is there a market?•Which sources are used?•What are the disciplinary needs?•What are the needs of different educational levels or types of organizations?•What are the obstacles and motivations?•How does picture seeking work?•What do users do with pictures?The discussion of these questions and the progress made toward answering them surfaces some problems with the existing state of research in this area:•The problem of isolating images•The student problem•The problem of studying the future•The problem of applying what we have learned•The problem of "user" as singular or plural.