A series of novel cationic polymers poly(hydroxyalkylene imines) were synthesized and tested for their ability to transfect cells in vitro and in vivo. Poly(hydroxyalkylene imines), in particular, poly(2-hydroxypropylene imine) (pHP), poly(2-hydroxypropylene imine ethylene imine) (pHPE), and poly(hydroxypropylene imine propylene imine) (pHPP) were synthesized by polycondensation reaction from 1,3-diamino-2-propanol and the appropriate dibromide. Electron microscopic examination demonstrated that the resulting polymers condensed DNA into toroid shape complexes of 100-150 nm in size. Transfection studies showed that all three polymers were able to deliver genetic material into the cell, with pHP being superior to pHPP and pHPE. pHP acted as an efficient gene delivery agent in a variety of different cell lines and outcompeted most of the widely used polymer or lipid based transfection reagents. Intravenous administration of pHP-DNA polyplexes in mice followed by the reporter gene analysis showed that the reagent was suitable for in vivo applications. In summary, the results indicate that pHP is a new efficient reagent for gene delivery in vitro and in vivo.