Milled black pepper (Piper nigrum) force-fed to Egyptian toads as a suspension in amphibian saline or injected subcutaneously in the dorsal lymph sac as an ethanol extract, induced primary tumours in the liver and secondary tumours in other organs (kidney and spleen). When applied to the skin of experimental animals as an ethanol extract, black pepper induced primary tumours in the liver and secondary tumours in the ileum and stomach. Tumours of the liver were diagnosed as hepatocellular carcinomas and those of the other organs as metastases of the primary liver tumours. It is speculated that one or more constituents of black pepper may be responsible for tumour induction in the organs of the Egyptian toad Bufo regularis.