  Quantum corrections to the magnetic central charge of the monopole in N=4
supersymmetric Yang-Mills theory are free from the anomalous contributions that
were crucial for BPS saturation of the two-dimensional supersymmetric kink and
the N=2 monopole. However these quantum corrections are nontrivial and they
require infinite renormalization of the supersymmetry current, central charges,
and energy-momentum tensor, in contrast to N=2 and even though the N=4 theory
is finite. Their composite-operator renormalization leads to counterterms which
form a multiplet of improvement terms. Using on-shell renormalization
conditions the quantum corrections to the mass and the central charge then
vanish both, thus verifying quantum BPS saturation.
