In the August issue of Nature Biotechnology, Francesca Sotrici and colleagues from the National Institute of Environmental Health Sciences describe how to commit the perfect murder (Nature Biotechnology 2001, 19:773-776). "Delitto perfetto" (Italian for perfect murder) is the name they gave to a two-step, cloning-free, technique that creates desired mutations, be they simple nucleotide replacements, precise insertions or large deletions. The first step involves integration of a counterselectable reporter (CORE) gene. The mutagenesis step involves elimination of the CORE cassette using designed oligonucleotides. The authors used the technique to create a series of insertions and deletion in the yeast genome. Delitto perfetto requires RAD52, which is implicated in homologous recombination. This approach has advantages over other mutagenesis strategies in that it reduces laborious subcloning or extensive sequencing.