The present publication provides guidance on the environmentally sound co-processing of hazardous wastes in cement kilns. The technical guidelines was adopted by the tenth meeting of the Conference of the Parties to the Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and their Disposal (decision BC-10/8) in October 2011. Co-processing of wastes in properly controlled cement kilns provides energy and materials recovery while cement is being produced, offering an environmentally sound recovery option for many waste materials. As countries strive for greater self-sufficiency in hazardous waste management, particularly in developing countries that may have little or no waste management infrastructure, properly controlled co-processing can provide a practical, cost effective and environmentally preferred option to landfill and incineration.