In this paper, Jeff Bonner of the St. Louis Science Center discusses the merits of formal versus naturalistic evaluation within the museum context. Bonner also presents the approach and findings of a two-part study designed to compare the results of these two evaluation approaches. They compared the the results of a formal analysis of the holding power, ease of use, readability of text, and overall enjoyability of nine exhibits with a naturalistic study focused on how one volunteer, two part-time employees and a staff supervisor viewed the same exhibits.