  Problems related to fermions, unitarity and chiral anomaly in high energy
electroweak interactions, are investigated. Particular attention is paid to the
correct functional integration over fermion fields in the background of
instanton-anti\-instanton type configurations. This leads to an expansion of
correlation functions in terms of a small parameter, $\rho/R$, when the
instanton-antiinstanton separation ($R$) is large compared to their sizes
($\rho$). Applying such a method to widely discussed cases of fermion-number
violation in the electroweak theory, we conclude that there are no theoretical
basis for expecting anomalous cross sections to become observable at energies
in the $10$ TeV region.
