Poly(beta-hydroxyalkanoates) (PRAs) are biodegradable polymers produced by a wide range of bacteria. The structures of these polymers may be tuned by controlling the available carbon source composition, but the range of functional groups accessible in this manner is limited to those that the organism is able to metabolize. Much effort has been made to chemically modify the side chains of these polymers to achieve new materials with new applications. We have previously reported the synthesis of the first cationic PHA, poly(beta-hydroxyoctanoate)-co-(beta-hydroxy-11-(bis(2-hydroxyethyl)-ami no)-10-hydroxyundecanoate) (PHON). Here, we report the use of this polymer as a plasmid DNA delivery system. PHON was found to bind and condense the DNA into positively charged particles smaller than 200 nm. In this manner, PHON was shown to protect plasmid DNA from nuclease degradation for up to 30 min. fit addition, treatment of mammalian cells in vitro with PHON/DNA complexes resulted in luciferase expression as the result of the delivery of the encoded gene.