Amphiphilic polycarbonate copolymers including methoxy-terminated poly(ethylene glycol)-co-poly (5,5-dimethyl trimethylene carbonate) [Poly(PEG-b-TMC)l and poly(ethylene glycol)-co-poly(trimethylene carbonate) [Poly(PEG-b-DTC)] were synthesized. The water-in-oil-in-water (W/O/W) solvent evaporation technique was adopted to produce anticancer magnetic Poly(PEG-b-DTC) microspheres containing tumor necrosis factor-alpha (TNF-alpha) genes and Fe3O4 magnetic ultrafine powder. Drug release studies showed that the microspheres can sustain a steady release rate of TNF-alpha genes in 0.1M phosphate buffer saline solution in vitro for up to 60 h. In vitro cytotoxicity assays demonstrated that the microspheres have high inhibition and antitumor action to human hepatocellular carcinoma (Bel-7204) cells in vitro. In vivo inhibition on the growth of hepatic carcinomas and histopathologic observation indicated that the microspheres possess a markedly high antitumor activity to human hepatocellular carcinoma (Bel-7204). (c) 2007 Wiley Periodicals, Inc.