Ph6Ge,0, and Me,GeCI has been studied a t 70 ev under high resolution, and that of the organogermanes ( o mtolyl),Ge, Ph,GeX (X = Me, PhCH,. CI, Br. and I), R6Ge, (R = Et, Ph, m-tolyl), (PhCH,),GeH, Me,GeH ,and GeCI, a t low resolution. Almost all the ion-current is carried by rnetal-containing ions and in general the most favoured fragmentation processes are those leading to even-electron ions.MASS spectroscopic studies have been reported for a variety of organo-silanes,l -stannanes,, and -plumbanes and the purpose of this paper is to present a similar study of a representative selection of organogermanes, and to draw attention to significant differences. Organogermanes the mass spectra of which have already been reported include Me,Ge,, Pri4Ge, Pri,GePrn, ( Pri2GeO),, Pri6Ge2,, (CHiC),Ge,5 and Et,GeR (R = CiCCHXH,, CiCCHXHCH,, CiCC(Me):CH,) and in addition some organogermanes have been identified from their molecularIn a preliminary communication lo we summarised the main features of interest observed in the mass spectra of organo-germanes and -stannanes.