Angiostatin and endostatin are proteins that inhibit both tumor growth and metastatic spread in vivo. Initial excitement over their use in anti-tumor therapy has been tempered recently due to difficulties in efficiently producing fully active recombinant proteins in sufficient quantities. Blezinger et al. now report a promising alternative: the direct injection of the gene encoding endostatin into muscle tissue, obviating the problems inherent to production of recombinant protein in microorganisms (see pp. 336 and 343).