Pyrolysis and oxidation characteristics of some biomass samples such as almond shell, walnut shell, hazelnut shell, tobacco waste, and rapeseed were investigated using Thermogravimetric Analysis (TGA) technique under slow heating conditions (20 K/min) from ambient to 1173 K. Pyrolysis experiments were carried out under dynamic nitrogen atmosphere of 40 mL/min. Dry air was used at the same rate in the oxidation experiments. The rates of mass losses from the biomass samples regarding temperature were obtained from the Differential Thermogravimetric Analysis (DTG) curves, and these rates were interpreted according to the pyrolysis and oxidation characteristics of the biomass samples. Since the heating rate was relatively very slow, individual peaks on the DTG curves resulting from the pyrolysis or oxidation of the major constituents that forming the complex structure of the biomass samples could be survived and distinguished from the thermograms. The maximum rates of mass losses (dm/dt)(max) from the oxidation experiments were determined to be higher than those from the pyrolysis experiments. On the other hand, the (dm/dt)(max) values were determined at about 550 K for pyrolysis, whereas they were below 500 K in case of oxidation irrespective of the type of the biomass samples.