The present investigation examined middle school students' evaluations of the usefulness for addressing a social studies inquiry question of a variety of sources of information, and the basis of these judgments. This task situation simulates an early phase of information gathering and selection in the context of inquiry. For each of nine sources, students were provided with, and asked to rate, the usefulness of six attributes (i.e. title, author, venue, date, type of publication, and a two-three sentence content summary) and the overall usefulness of each source. The sources varied in usefulness as determined by expert ratings. Students' overall ratings showed that some clearly differentiated the usefulness of the sources while others did not. Analyses of the ratings of individual attributes indicated that "higher" differentiators primarily considered content indicators (i.e., title and summary) when making usefulness judgments; "lower" differentiators considered author and venue of publication, with much less emphasis on source content. Discussion focuses on the instructional and practical implications of skill at differentiating more from less useful sources of information during initial information gathering and selecting in the context of 21st century Internet resources. (Contains 4 tables.)