  We examine several issues related to the processes of Dirac
monopole-antimonopole production in high-energy collisions such as $e^+e^-$
annihilation. Perturbative calculations for such processes are known to be
inherently ambiguous due to the arbitrariness of direction of the monopole
string; this requires use of some prescription to obtain physical results. We
argue that different prescriptions lead to drastically different physical
results which suggests that at present we do not have an entirely satisfactory
procedure for the elimination of string arbitrariness (this problem is quite
separate from the problems caused by the large coupling constant). We then
analyze the consequencies of discrete symmetries (P and C) for the monopole
production processes and for the monopole-antimonopole states. The P and C
selection rules for the monopole-antimonopole states turn out to be different
from those for the ordinary fermion-antifermion or boson-antiboson system. In
particular, the spin 1/2 monopole and antimonopole should have the same
helicities if they are produced through the one-photon annihilation of an
electron and positron. A stronger selection rule holds for spinless monopoles:
CP symmetry absolutely forbids the monopole-antimonopole production through the
one-photon annihilation of an electron and positron. Single-photon $e^+e^- \to
g^+g^-$ amplitude has been a key input in calculating the contribution of
virtual $g^+g^-$ pairs to various physical processes such as the decay $Z\to
3\gamma$ and the anomalous magnetic moment of the electron. Applying our
conclusions to these cases can lead to significant modifications of the results
obtained in previous works.
