  We discuss properties of D-brane configurations in the matrix model of type
IIB superstring recently proposed by Ishibashi, Kawai, Kitazawa and Tsuchiya.
We calculate central charges in supersymmetry algebra at infinite N and
associate them with one- and five-branes present in IIB superstring theory. We
consider classical solutions associated with static three- and five-branes and
calculate their interactions at one loop in the matrix model. We discuss some
aspects of the matrix-model formulation of IIB superstring.
