The complexes formed by DNA or RNA interacting with polycations have been widely used as non-viral gene vectors. Owing to the strong and long-ranged electrostatic interaction

the complex is usually controlled by kinetics and its structure evolves with time. This review summarized the recent studies on kinetics of the complexation between DNA/RNA with polycations. We proposed that the major factors determining the kinetics of complexation were the balance between the long-ranged electrostatic repulsion force and the short-ranged electrostatic attraction forces

as well as the intra- and inter- complex disproportionation rate. The disclosure of the complexation mechanism is helpful in developing high performance gene delivery vectors.