  We study a supersymmetric extension of the Virasoro algebra on the boundary
of the anti-de Sitter space-time AdS_{3}. Using the free field realization of
the currents, we show that the world-sheet affine Lie superalgebras
osp(1|2)^{(1)}, sl(1|2)^{(1)} and sl(2|2)^{(1)} provide the boundary N=1,2 and
4 extended superconformal algebras, respectively.
