  Radiative corrections to processes that involve the production and subsequent
decay of unstable particles are complex due to various theoretical and
practical problems. The so-called double-pole approximation offers a way out of
these problems. This method is applied to the reaction $e^{+}e^{-} \to
W^{+}W^{-} \to 4 $fermions, which allows us to address all the key issues of
dealing with unstable particles, like gauge invariance, interactions between
different stages of the reaction, and overlapping resonances. Within the
double-pole approximation the complete $\OO(\alpha)$ electroweak corrections
are evaluated for this off-shell $W$-pair production process. Examples of the
effect of these corrections on a number of distributions are presented. These
comprise mass and angular distributions as well as the photon-energy spectrum.

High Energy Physics - Phenomenology