Abstract Isolated GeH stretching frequencies are reported or derived from earlier work for 51 substituted germanes in the gas phase, the substituents including Me, Et, i-Pr, CF 3, Ph, CN, C 2H and X = F, Cl, Br, I. In a number of cases, very small positive stretch-stretch interaction force constants are obtained which reflect the virtual decoupling of bond stretching motions in GeH 3 or GeH 2 groups where the bonds differ but slightly in strength. This may be described as ‘local mode’ behaviour, in the fundamental region. β effects of Me, X and lone pairs of electrons are found which produce conformational variations in ν isGeH comparable with those found in carbon analogues. These may be used inter alia to study conformer abundancies. Solid state spectra of GeH 3NCO and GeH 3NCS suggest that both of these have non-linear skeletons in this phase.