We report the synthesis of a low cytotoxic polycation that maintains its cationic strength for well over a few hours then degrades into a benign polymer with nontoxic byproducts. Well-defined poly(2-dimethylaminoethyl acrylate) (PDMAEA) of five different molecular weights prepared using reversible addition-fragmentation chain transfer (RAFT) living radical polymerization degrades slowly over 200 h ( 8 days). As this degradation is independent of both the polymer molecular weight and solution pH, it is consistent with a self-catalyzed hydrolysis process without the need for an internal or external degradation trigger. In addition, the polymer shows little or no cytotoxicity to HeLa cells for the molecular weights of 5600 and below, even at very high polymer concentrations (equivalent to a nitrogen/phosphorus ratio of 200). Therefore, at sufficiently low molecular weights this polymer has the essential attributes (i.e., ability to autodegradable and low toxicity) for a delivery carrier suitable for DNA or siRNA.