  The complete electroweak O(alpha) corrections are calculated for the
charged-current four-fermion production processes e+e- --> nu_tau tau+ mu-
anti-nu_mu, u anti-d mu- anti-nu_mu, and u anti-d s anti-c. The calculation is
performed using complex gauge-boson masses, supplemented by complex couplings
to restore gauge invariance. The evaluation of the occurring one-loop tensor
integrals, which include 5- and 6-point functions, requires new techniques.
Explicit numerical results are presented for total cross sections in the energy
range from the W-pair-production threshold region up to a scattering energy of
2TeV. A comparison with the predictions based on the "double-pole
approximation" (DPA) provided by the generator RacoonWW reveals corrections
beyond DPA of < 0.5% in the energy range 170-300GeV, in agreement with previous
estimates for the intrinsic DPA uncertainty. The difference to the DPA
increases to 1-2% for sqrt{s} = 1-2TeV. At threshold, where the DPA becomes
unreliable, the full O(alpha) calculation corrects an improved Born
approximation (IBA) by about 1.6%, also consistent with an error estimate of
the IBA.
