During the period between 1967 and 1983, there were 28 WDHA patients in Japan. Clinically, these patients were not very different from those reported in western countries, but we have been able to add a few observations as follows. First, the WDHA patients with pancreatic endocrine tumors and those with neuroblastic tumors were present in almost equal numbers. Second, fluctuating hypercalcemia was often observed in patients with this syndrome, but it was not observed in any watery diarrhea due to the other etiologies. Third, the WDHA patients who have multiple endocrine neoplasia (MEN) type 1 have multiple tumors in the pancreas, indicating that the patients with MEN should be managed in a different manner in regard to determining tumor location as well as applying surgical treatment. When various types of tumors were examined for VIP content, it was found that many tumors have the potential to produce VIP, and when VIP is produced in large amounts, plasma VIP levels become elevated, resulting in the WDHA syndrome.