Publisher Summary Echinococcus multilocularis was definitively established as an independent species by Vogel's exact morphological and biological investigations, including the completion of the life cycle of the parasite in experimentally infected hosts. The natural life cycle of E. multilocularis is uniform, although the host assemblages universally differ in accordance with faunal changes southwards from the Arctic. This fact is the principal determinant of the prevalence and distribution of the parasite. Attempts to delineate the three approximate geographical ranges of E. multilocularis have been made but exact distributional data are incomplete. Nevertheless, the geographical distribution of E. multilocularis seems to be uniquely restricted to the northern hemisphere. Alveolar echinococcosis (AE) of humans is biologically comparable to the disease in the natural intermediate hosts. The primary localization of E. multilocularis metacestodes (larvae) in humans (as well as in natural intermediate hosts) is almost exclusively in the liver. Local extension of the lesion and metastatic lesion formation in the lungs, brain, and other organs can follow. This chapter presents the immunological aspect of E. multilocularis and also discusses various diagnostic techniques. New developments in the diagnosis of and vaccination against E. multilocularis are also discussed, but the major and crucial aspect remains concentrated on the identification of E. multilocularis antigens to protect hosts.