In recent years, trials to reuse fused slags, obtained through the further treatment of incinerated ash produced in the process of the disposal of garbage or sewer sludge, such as for building materials including bricks, have drawn attention. To establish the safety of using such substances, elution tests for metals and metal contents were investigated in this study. As the result of examining 13 slags, which were made by different methods, little elution of toxic metals was found in the elution tests when water was used as a solvent. However when acid was used, there was a tendency for the elution of many kinds of metals to become greater. On other hand, the results of content measurements showed that arsenic and selenium, which were not seen to be eluted from any of the slags tested, were detected; and that aluminum and manganese existed in the slags in high concentrations.