The main by-product of the steel industry is slag whose production is functional to that of the steel itself. This work aims to analyze the cases of industrial symbiosis implemented in various countries with particular attention to the exchange of slag which, from steel mill waste, becomes a secondary raw material for other industrial sectors. In all, 12 cases of scientific literature relating to industrial areas were analyzed, and classified in function of the type of slag (deriving from different production processes). The final application of the slags is studied in terms of receiving sector and the barriers to the implementation of industrial symbiosis. It was found that the cement and road constructions industries are the main symbiotic receiving partners. In the scientific literature the reuse of slag is extensively studied in cases of integrated cycle steel production, while the case studies involving electric furnace slag are much more limited.