The supersymmetry properties of the asymptotically anti–de Sitter (adS) black holes of Einstein theory in 2+1 dimensions are investigated. It is shown that (i) the zero-mass black hole has two exact supersymmetries; (ii) extreme lM=‖J‖ black holes with M≠0 have only one; and (iii) generic black holes do not have any. It is also argued that the zero-mass hole is the ground state of (1,1) adS supergravity with periodic (‘‘Ramond’’) boundary conditions on the spinor fields.

• Received 29 October 1993

DOI:https://doi.org/10.1103/PhysRevLett.72.183