CHS 828, a cyanoguanidine with potent experimental antitumoural activity, inhibits activation of nuclear factor-kappaB. In the present study, marked antitumoural activity of peroral CHS 828 was shown against three different human neuroendocrine tumours, midgut carcinoid (GOT1), pancreatic carcinoid (BON), and medullary thyroid carcinoma (GOT2), transplanted in nude mice. Our results indicate that CHS 828 can be a candidate drug for treatment of neuroendocrine tumours.