The Knudsen effusion mass spectrometric method was used in measuring the partial pressures of GeC2, Ge2C, Ge3C, and Ge2C2 above liquid germanium which was contained in a graphite Knudsen cell. These partial pressures have been combined with calculated thermal functions to determine the atomization enthalpies, Delta H-2,H-0,H- (in kJ mol(-1)) : 1197 +/- 10 (GeC2); 902 +/- 22 (Ge2C); 1247 +/- 22 (Ge3C); and 1535 +/- 25 (Ge2C2). The enthalpies of formation, Delta H-f,H-0,H- (in kJ mol(-1)) are 597 +/- 10 (GeC2); 552 +/- 12 (Ge2C); 579 +/- 22 (Ge3C); and 630 +/- 25 (Ge2C2).