Endocrine tumors of the pancreas apparently develop from a premature stem-cell, possibly originating from the ectodermal neural crest. These tumors belong to the APUD-cell system, which is identical with the "Helle-Zellen-system". Following a description of the various forms of appearance there is a discussion of the different syndromes. The present-day differentiated diagnostic procedures are described. Finally, details and problems of treatment, especially regarding surgical intervention, are discussed. Cases from the author's own clinic are considered.