Genetically modified marmosets. The common marmoset (Callithrix jacchus) was genetically modified using of a self-inactitvating lentiviral vector. This procedure results in transgenic common marmosets that expressed the transgene in several organs. Germline transmission of the transgene was achieved and the transgenic offspring developed normally. The transgenic marmosets are a new animal model for human disease and will be valuable to many fields of biomedical research. This short note is based on the paper by Sasaki et al. Nature 459, 523-527, 2009.