  In this paper D-brane boundary states constructed in Gepner models are used
to analyze some aspects of the dynamics of D0-branes in Calabi-Yau
compactifications of type II theories to four dimensions. It is shown that the
boundary states correspond to BPS objects carrying dyonic charges. By analyzing
the couplings to closed string fields a correspondence between the D0-branes
and extremal charged black holes in N=2 supergravity is found.
