The two lowest-lying (H-bridged, cyclic) electronic states (B-2(1) and (2)A(1)) of the disilaethynyl (SiSiH) radical have been investigated using ab initio electronic structure theory. Theoretical methods through the full coupled cluster with all triple excitations (CCSDT) have been used, and basis sets as large as Dunning's correlation consistent pentuple set adopted. While the SCF, MP2, CISD, and CCSD levels of theory predict the B-2(1) state to be lower in energy, the CCSD(T) and CCSDT methods show that the (2)A(1) state is the true electronic ground state. With our most reliable method, the energy difference is predicted to be T-e(B-2(1))=0.60 kcal/mol (0.026 eV,210 cm(-1)) and T-0(B-2(1))=0.37 kcal/mol (0.016 eV,128 cm(-1)). This theoretical finding confirms the experimental assignment by Xu [J. Chem. Phys. 108, 7645 (1998)] in 1998 that the ground state of SiSiH is the (2)A(1) state and it is 0.020 +/-0.005 eV lower in energy than the B-2(1) state.