The wastewater coming from a tannery activity is often treated by biological treatment; the sludges produced by these processes are largely disposed off in landfill. The tannery sludge is currently a big ecological and environmental problem because of its high content of organic compounds and heavy metals, mainly Crome. The research work presents the possibility of an aerobic stabilization of sludges or a mixture of sludge and other materials with high content of organic compounds. The results show an initial phase of fast increasing of temperature due to a high bacterial activity. This high activity decreases quite soon and it becomes stabilized at mesophilic conditions. The final conditions of the sludge show a reduction of water content, a reduction of Total Volatile Solids (TVS) and an improvement of biological stability.