  We re-investigate the question whether a light higgsino-like neutralino is a
viable Dark Matter candidate. To this end we compute the dominant one-loop
corrections to the masses of the higgsino-like states in the minimal
Supersymmetric Standard Model (MSSM), due to loops involving heavy quarks and
their superpartners. We also calculate analogous corrections to the couplings
of higgsino-like neutralinos to Z and Higgs bosons. In the region of parameter
space leading to high higgsino purity of the lightest neutralino, these
corrections can change the expected relic density by up to a factor of five in
either direction. We conclude that for favorable choices of soft supersymmetry
breaking parameters, a state with more than 99% higgsino purity could indeed
form all cold Dark Matter in the Universe. In some cases these corrections can
also increase the expected cross section for LSP scattering off spinless nuclei
by up to two orders of magnitude, or reduce it to zero.
