This paper presents ab initio values for the “paramagnetic” orbital contributions J1b to the spin-spin coupling constants of the molecules methane, water, hydrogen fluoride, hydrogen cyanide, hydrogen isocyanide, acetylene, ethylene, ethane, acetonitrile, and methyl isocyanide. These values are compared with those obtained from previous semiempirical studies. © 1979, American Chemical Society. All rights reserved.