A series of dialdehyde cellulose samples with varied aldehyde content were prepared, and they were further converted to nitrogen-containing derivatives by Schiff base reaction with hydroxylamine or hydrazine. Thermal decomposition of these compounds in nitrogen was studied by thermogravimetry/differential thermal analysis (TG/DTA). While the decomposition of unmodified cellulose in nitrogen started at about 280 degreesC and rapid weight loss occurred at 300-330 degreesC, the introduction of dialdehyde groups to cellulose resulted in significant shifts of decomposition to the lower temperature side. The samples of high degree of substitution showed two-step decomposition at around 220 and 280 degreesC, indicating a basic change in the mode of decomposition. The nitrogen-containing derivatives showed changes in thermal decomposition similar to that of dialdehyde cellulose, hut the samples with high degrees of substitution, above similar to 70%, showed an explosive decomposition at 151-162 degreesC. This anomalous phenomenon stems characteristic to the chemical structures involving C=N-N or C=N-O groups.