A limited body of research examines the extent to which social studies teachers are actually utilizing primary sources that are accessible in traditional classroom-based formats versus web-based formats. This paper initiates an exploration of this gap in the literature by reporting on the result of a survey of secondary social studies teachers, all members of the National Council for the Social Studies, that examines the extent to which these social studies teachers are using classroom and web-based primary sources. In particular we ask: To what extent has the availability of web-based primary sources impacted social studies teachers' use of primary sources in the classroom? In order to investigate the above question successfully, we examine the following supporting questions: How are social studies teachers using classroom-based primary sources? How are social studies teachers using web-based primary sources? While the study reveals teachers' understandings of the potential for using primary sources to support historical inquiry and the potential of the web for providing access to previously inaccessible primary sources, the teachers' actual use of both classroom-based and web-based primary sources seems limited. (Contains 15 tables.)