The development of efficient methods to transfer genes into eukaryotic cells is important for molecular biotechnology. A number of different technologies to mediate gene transfer have been developed over the last 35 years, but most have drawbacks such as cytotoxicity, low efficiency and/or restricted applicability. Activated polyamidoamine (PAMAM)-dendrimers provide a new technology for gene transfer that offers significant advantages over classical methods. Reagents based on this technology provide high gene transfer efficiencies, minimal cytotoxicity, and can be used with a broad range of cell types. This technology could also be useful for in vivo gene transfer in gene therapy applications.