  In the Minimal Supersymmetric Standard Model (MSSM) the masses of the
neutralinos and charginos depend on the gaugino and higgsino mass parameters M,
M' and $\mu$. If supersymmetry is realized, the extraction of these parameters
from future high energy experiments will be crucial to test the underlying
theory. We present a consistent method how on-shell parameters can be properly
defined at one-loop level and how they can be determined from precision
measurements. In addition, we show how a GUT relation for the parameters M and
M' can be tested at one-loop level. The numerical analysis is based on a
complete one-loop calculation. The derived analytic formulae are given in the
appendix.
