Numerical calculations using the Holstein-Hubbard model show that stable bipolarons can form in homogeneous DNA duplexes. Since matrix elements of the Hamiltonians are different, the phase diagram determining the bipolarons stability for a G/C duplex differs from that for an A/T duplex. It is shown that a bipolaron superconductivity with the transition temperature T-c = 6 - 20 K can take place in DNA, and the transition temperature depends on the parameter values of the model. The bipolaron model can serve as a basis for explaining experiments on DNA superconductivity. (C) 2011 Elsevier B.V. All rights reserved.