This paper examines the archival potential of blogs, a popular form of electronic record in which personal accounts and commentaries are entered regularly in an on-line journal. A historical survey of the diary—the blog's paper-based antecedent—suggests how the two records are alike and where they diverge, taking into account their evidential values, their seemingly contradictory public and private qualities, and their very diverse physical natures. The paper discusses the role that traditional archives should play in preserving blogs, while considering the implications that their loss would have for our cultural memory, and offering some suggestions for ensuring their preservation.