The attachment of labels onto DNA is of utmost importance in many areas of biomedical research and is valuable in the construction of DNA-based functional nanomaterials. The copper(I)-catalyzed Huisgen cycloaddition of azides and alkynes (CuAAC) has recently been added to the repertoire of DNA labeling methods, thus allowing the virtuallyunlimited functionalization of both small synthetic oligonucleotides and large gene fragments with unprecedented efficiency. The CuAAC reaction yields the labeled polynucleotides in very high purityafter a simple precipitation step. The reviewed technology is currentlych anging the wayin which functionalized DNA strands are generated cost-efficientlyin high qualityfor their application in molecular diagnostics systems and nanotechnological research.