Ab initio equation-of-motion coupled cluster (EOM-CCSD) calculations have been performed on a set of 44 complexes to obtain one-bond H-Y spin-spin coupling constants ( 1 h J H - Y ) across X-H-Y hydrogen bonds, with Y as the second-period elements 1 5 N, 1 7 O, and 1 9 F. For complexes with traditional hydrogen bonds, the reduced Fermi-contact terms and the reduced one-bond spin-spin coupling constants ( 1 h K H - Y ) are negative. Since 1 K X - H has been shown previously to be positive, a change of sign of these two coupling constants must occur along the proton-transfer coordinate. For complexes with symmetric X-H-X hydrogen bonds, the two reduced X-H coupling constants are equal and positive at equilibrium. For complexes stabilized by hydrogen bonds that have some proton-shared character, both 1 h K H - Y and 1 K X - H are also positive. The signs of all three reduced coupling constants ( 1 h K H - Y , 2 h K X - Y , and 1 K X - H ) that can arise between pairs of hydrogen-bonded atoms are interpreted in terms of the nuclear magnetic resonance triplet wave function model (NMRTWM). Determination of the signs of 1 h K H - Y and 1 K X - H could be useful for confirming the presence or absence of a proton-shared hydrogen bond.