Adsorption studies of digermane (Ge2H6) and disilane (Si2H6) on Ge(100) are reported. Temperature‐programmed desorption (TPD) experiments suggest the existence of two hydrogen adsorption states in the submonolayer regime for both digermane and disilane. The TPD spectra observed for disilane on Ge(100) are qualitatively similar to previous studies of disilane adsorbed on thin epitaxial layers of germanium on Si(100). These spectra show the existence of an α‐state arising from the germanium monohydride and a β1‐state arising from a silicon monohydride. The two‐peak structure observed in the hydrogen TPD spectra for digermane on Ge(100) suggests the existence of both germanium monohydride and germanium dihydride, about which there is disagreement in the literature. However, high‐resolution electron energy‐loss spectroscopy and low‐energy electron diffraction provide additional evidence for the existence of both germanium hydrides on the digermane/Ge(100) system. Kinetic energy distributions of electronically desorbed H+ and hydrogen removal cross‐sections obtained through electron‐stimulated desorption are also presented for both systems. Copyright © 2000 John Wiley & Sons, Ltd.