Black stone has been used since Antiquity to treat snake bites and local infections. Its efficacy is debated. Since no clinical trial has been performed, we conducted a series of in vivo and in vitro experiments in a murine model. After determining the LD50 of batches of venoms of Bitis arietans, Echis ocellatus and Naja nigricollis according to the Spearman-Kärber's method, we used four separate methods. First, we injected a fixed lethal amount of venom (triple the LD50) IM to the shaved thighs of lots of five mice and applied the black stone with an adhesive plaster at the point of injection at 0, 15, 30, 60 and 180 minutes. In another series of experiments, we administered increasing amounts of venom to each group of 5 mice according to the same protocol used to measure the LD50; and applied black stone as above, immediately after the administration of each amount of venom. In the third series of experiments, we reduced black stone to powder and mixed 3 LD50 of each venom with an increasing amount of powder for 30 minutes. After centrifugation, the supernatant was injected into mice and mortality measured. Two control groups (venom alone and black stone alone) were used in all the cases. Venom adsorption on black stone surface was assessed in vitro by measurement of residual proteins in supernatant after mixing black stone powder and venom for thirty minutes and centrifugation. The results showed the absence of effectiveness of the black stone when applied on wounds after venom injection. However, the direct contact between the black stone powder and the venom did reduce venom toxicity, as if black stone fixed venom proteins and removed the venom from the inoculum. The mechanical effectiveness of black stone can thus be shown. However, its efficacy in treating envenomation seemed very doubtful because of it is very nonspecific and because the venom diffuses rapidly from the wound.