The successful delivery of nucleic acids to particular target sites is the challenge that is being addressed using a variety of viral and nonviral delivery systems, both of which have distinct advantages and disadvantages. Nonviral vectors offer the advantage of safety and flexibility over viral vectors, although they lack efficiency. Dendrimers are novel, three-dimensional polymers that have the ability to interact with various forms of nucleic acids such as plasmid DNA, antisense oligonucleotides, and RNA to form complexes that protect the nucleic acid from degradation. The interaction between the dendrimers and the nucleic acids is purely electrostatic where the cationic dendrimer condenses the anionic nucleic acids. Because cell membranes are negatively charged, the net positive charge of the dendrimer nucleic acid complex determines the transfection efficiency, although highly cationic systems are also cytotoxic. The nature of the dendrimer nucleic acid complex depends on various factors like stoichiometry, concentration of dendrimer-amines and nucleic acid-phosphates, as well as bulk solvent properties like pH, salt concentration, buffer strength, and dynamics of mixing. This article aims to review the role of dendrimers as novel gene delivery vectors both in vitro and in vivo. Dendrimer-based transfection reagents have become routine tools for in vitro transfection, but in vivo delivery of therapeutic nucleic acids remains a challenge. BACKGROUND This review discusses the role of dendrimers as novel gene delivery vectors both in vitro and in vivo. Dendrimer based transfection reagents have become routine tools for in vitro transfection but in vivo delivery of therapeutic nucleic acids remains a challenge.