By a trivial modification of Hawking’s well-known topology theorem for black holes, one can obtain a lower bound of4&pgr;(g−1)/−&Lgr;for the area of an apparent horizon of genusgin a vacuum spacetime with cosmological constant&Lgr;<0.We discuss a derivation in the special case of an apparent horizon at a moment of time symmetry, so that the horizon is a minimal surface. ©1999 American Institute of Physics.