The 5,7-dichloro, 5,7-dibromo, 5,7-diiodo and 5,6-dinitro derivatives of oxine (ligands L1-L4) were used to prepare uranyl chelates (A t-A4). Thermal analysis (DTA) and mass spectroscopic studies were performed. The stoichiometries of the chelates were determined by elemental analysis, molecular weight determination applying an r liquid scintillation counter and mass spectral measurements. The uranyl:ligand ratios were found to be 1 :l for A1, 1:3 for A2, 1:2 (monohydrate) for A3, and 1:2 for A 4. The correlation between the thermal analysis and mass spectra was examined. The activation energy required for each step of thermal degradation of the ligands and chelates was calculated. The natures of most of the molecular ions obtained in the mass spectra were also explained.