Book excerpt: This publication combines and extends the now classic system of human cytogenetic nomenclature prepared by expert committees and published in collaboration with Cytogenetic and Genome Research (formerly: Cytogenetics and Cell Genetics ) since 1963. Revised and finalized by the ISCN Committee and its advisors at a meeting in Vancouver, BC, in December 2004, it updates, corrects and incorporates all previous human cytogenetic nomenclature recommendations into one systematically organized publication. It thus supersedes the previous compilations in ISCN 1985 and its supplement, ISCN 1991 , the Guidelines for Cancer Cytogenetics , and ISCN 1995 . What s new in ISCN 2005? the G- and R-banded karyotypes have been replaced by new ones reflecting higher band-level resolutions new ideograms at the 300-band and 700-band level have been added the in situ hybridization nomenclature has been modernized, simplified, and expanded new examples reflecting unique situations are included a basic nomenclature for recording array comparative genomic hybridization results is introduced ISCN 2005 also contains a detachable fold-out of the normal human karyotype, consisting of photographs of G-banded and R-banded chromosomes at the commonly examined 550-band resolution stage and their diagrammatic representations a useful aid for human cytogeneticists, technicians, and students.