Transposable elements are powerful engines of evolution. They constitute the majority of genomic DNA in many eukaryotes, and they dramatically shape genetic content by causing mutations, rearrangements and sequence duplications. Of increasing significance is the link of these transposon-mediated mutations to disease. Sequencing of human populations demonstrates that active transposons are substantially more prevalent than previously appreciated. The aims of this conference are to: 1) Apply recent innovations in high-throughput sequencing and genome analysis to the study of transposon biology and genome evolution; 2) Discuss the discovery of cellular systems that inhibit transposon activity as examples of the evolutionary arms race that exists between mobile DNA and their hosts; and 3) Describe active transposition during neurogenesis and in tumor cells and raise fundamental questions about the role of mobile DNA in brain development and cancer. The symposium is designed to foster ties between leaders in the field of transposon biology and the pioneers of genome analysis. Discussions of transposon activity and genome evolution will focus on mechanistic models. Methods applied to these problems include molecular structures, biochemistry, expression studies and bioinformatic analyses. The transposons and hosts represented in this meeting include diverse examples from eubacteria, archaea, protists, plants and mammals.