Top and Bottom at Threshold: Recent Results

Recent results obtained for the systems of two heavy quarks are discussed. In particular, we consider phenomenological applications for the third-order results for the energy levels and wave function. Special emphasis is put on the resummation of potentially large logarithms in the velocity of the heavy quarks. Predictions for the mass of the ηb meson are dicussed which still has to be confirmed experimentally. Furthermore, the ratio of the photon mediated production or annihilation rates of spin triplet and spin singlet heavy quarkonium states are considered.