Recycling of spent lead-acid batteries is leading to the production of slag which may be classified as hazardous waste because of its toxicity or lead (Pb) content. The leaching behavior of metals in the raw and solidification/stabilization (S/S) applied slag samples is evaluated with the toxicity characterization leaching procedure (TCLP). Then, TCLP results are compared to the threshold values given in USEPA Method 1311: 1992 and EU standard EN12457-4 2002 which suggest different pH values for TCLP. Raw slag sample were classified as hazardous waste according to USEPA and as non-hazardous according to EU-EN. The blocks which are produced by S/S applied slag with cement (slag ratio 25%-B25L and 50%-B50L) are classified as non-hazardous according to USEPA Method. However, the overall toxicity of blocks for B50L is classified as highly acute toxic (TU > 100 class 4). Therefore, B25L can be reused in the construction since it is not toxic and classified as high-quality concrete. It is suggested that appropriate waste management should be as follows: (1) spraying the acid solution to slag heap and collecting drained water in coagulation/flocculation tank, (2) recovery of lead (%3.3-4.0 Pb) and significant amount of iron (%18-25 Fe) from dried sludge and return to furnace and (3) S/S to slag for safer disposal to landfill or reuse of blocks as construction materials. Moreover, the results showed that toxicity test is a more convenient criterion to designate hazardous waste since it is directly reflecting the hazardous characteristics of waste.