Carcinoid tumors are rare, indolent neoplasms that, although clinically well defined, are regarded as exotic and are consequently often unrecognized. Although little is known of the lives of the men who defined the tumor, described its distinct histology and cell type, and delineated the clinical hallmarks of the disease even less is known of the pathobiology of the lesion. In the nineteenth century, T. Langhans (1839-1915), O. Lubarsch (1860-1933), and W. B. Ransom (1860-1909) described unusual tumors in the small bowel but each failed to adequately investigate these novel entities. This responsibility fell to Siegfried Oberndorfer (1876-1944), who became the first to adequately characterize the nature of the tumors and refer to them as "benign carcinomas." During his tenure at the Pathological Institute of the University of Munich, Oberndorfer noted in 1907 that the lesions were distinct clinical entities and named them "karzinoide" ("carcinoma-like"), emphasizing in particular their benign features. In 1929 he amended his classification to include the possibility that these small bowel tumors could be malignant and also metastasize. Although the enterochromaffin cell, the carcinoid cell of origin, had been identified as early as 1897 by N. Kulchitsky (1856-1925), it was not until 1953 that F. Lembeck (1922-) established that such cells synthesized and secreted serotonin--a potent bioactive amine. Thereafter the protean clinical effects of serotonin, including "flushing," were recognized as was the associated relationship of carcinoid heart disease (Biörck in 1952) and fibrosis (Moertel in 1961). As the centennial of the observations of Oberndorfer approaches, it should be noted that the legacy of one of Germany's most distinguished pathologists, teachers, and scientists (whose career fell victim to the machinations of the Third Reich) has been largely unrecognized. Similarly, the biology and mechanistic analysis of these lesions remain to a large extent unexplored. The present article describes the contributions of the clinical and scientific pioneers in the elucidation of carcinoid disease and traces the evolution of the discovery and understanding of carcinoid tumor biology. It also serves to memorialize the extraordinary accomplishments of Oberndorfer, whose vision exceeded his times.