Based on the known positive sign of 1Jca or of the one-bond reduced coupling constant 1 K XH magnitudes and signs of geminal and vicinal coupling constants 2J HXH , 2J CXH , 2J CXC , and 3J HXCH (X = C, Si, Ge, Sn, Pb) are investigated by homo- and heteronuclear double resonance in group IV hydrides XH4 and some alkyl-, phenyl-, and halogen-substituted derivatives. 2J HH , 2J CH , and 2J CC increase strongly with the atomic number of X, while there is a less strong but systematic dependence on substitution. 3 J HH is positive and decreases with the atomic number of X. These observations are discussed using existing theories of spin coupling. Chemical shifts and isotope effects on chemical shifts and coupling constants are reported.