Particular DNA sequences have long been known to have exceptional structures and biological properties. Famous in the medical world are the trinucleotide repeat sequences, such as (CTG)(n), and their association with more than a dozen neurodegenerative diseases. Numerous meetings have been held to discuss these repeats and the diseases they cause. Now, a much-needed meeting has been held to discuss other noncanonical (non-B-form) DNA structures, their properties, and their biological consequences. Although the meeting was titled "DNA palindromes: roles, consequences, and implications of structurally ambivalent DNA," the participants discussed and debated a range of additional structures-dubbed "Z," "HJ," "G4," and "H" DNA-as well as trinucleotide repeats. These remarkable structures can have profound effects on chromosomes and organisms, ranging from mutational hotspots in bacteria to causes of intellectual disability in humans. Bringing together four dozen researchers prominent in the field focused attention on these controversial DNA structures in a way that promises to spur greater understanding of DNA elements critical to life and health.