The dissociation energies of the gaseous monosulphides GeS, ScS, YS, LaS and CeS were determined : D°0(GeS)= 130.9±0.6; D°0(ScS)= 113.4±2.5; D°0(YS)= 125.7±2.5; D°0(LaS)= 137.5±2.5; and D°0(CeS)= 136.0±3.0 kcal/mole. In an appendix, selected values for the dissociation energies of the monoxides ScO, LaO, YO, CeO and VO are given: D°0(ScO)= 160.4±2.0; D°0(YO)= 170.4±2.5; D°0(LaO)= 190.3±2.5; D°0(CeO)= 188.6±3.5 and D°0(VO)= 148.8±2.5 kcal/mole.