The spent lining of electrolysis pots is the main source of solid wastes in the production of aluminium. Being contaminated by cyanides, they may cause serious environmental problems for ground and surface waters. They have to be disposed of as special waste, or decontaminated prior to final disposal. This paper described the removal of free and complex cyanides from the spent pot lining waste by thermal hydrolysis. In addition, fluorides in the hydrolysis filtrate were precipitated by Ca(OH)(2) and disposed of together with the hydrolysed spent pot lining material.