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Actiniaria, Corallimorpharia, Zoanthidae and Ceriantharia belong to the most neglected marine taxa. Habitats that were difficult to access in the past, complicated and doubtful \nmethods for identification, the lack of summarizing literature and the lack of specialists led soft-bodied hexacorals into a dramatic and increasing under-representation in both biodiversity assessments and in ecological studies. The taxonomic state of knowledge for this group is far behind this of other taxa of comparable importance. This global description of the situation is especially valid for the South East Pacific. Therefore important aspects of systematic work with soft-bodied hexacorals have been addressed in the presented dissertation and exemplified by Chilean sea anemones. The results have been presented in specialist journals and at relevant meetings. To fill existing gaps and to alleviate difficulties, traditional procedures have been combined with modern methods. The applied techniques were tested for their expenditure/benefit ratio. On this base a novel, efficient approach for systematic studies of soft-bodied hexacorals was elaborated. With this approach one of the most common shallow-water sea anemones of north and central Chile, which spread out remarkably during the last decades, was described as Anemonia alicemartinae. The two most common shallow-water sea anemone species of the south east Pacific, Phymactis papillosa and Phymanthea pluvia, were re-described and fundamentally revised. The four south-hemispheric genera Isoulactis, \nIsocradactis, Saccactis and Oulactis, which exhibit extraordinary morphology, were revised and put together in the genus Oulactis. The deep-water genus Actinostola was revised and the species Actinostola chilensis was re-described. Traditionally used characteristics to distinguish species of the genus Actinostola were critically tested and new, alternative features were proposed. The discovery of a colonial sea anemone disproved the common idea of Actiniaria as a purely solitary group. The phenomenon of coloniality in sea anemones was described in detail and phylogenetic consequences were discussed. Some biomechanical and evolutionary-ecological hypotheses, which were used to explain the absence of colonial sea anemones, were questioned by this discovery. The reproductive strategies of the addressed Chilean sea anemone species were summarized and appearance, habitat, bathymetric distribution and reproductive mode were compared. Existing hypotheses about links between these parameters were tested and discussed. A hypothesis on spreading tendencies of some Chilean sea anemone species was elaborated. The effects on populations of other invertebrates, especially on those of economic importance, were discussed on the basis of some examples. The distribution of Chilean species and their relation to the South West Atlantic and the Antarctic fauna was analysed and the discovered zoogeographic patterns were discussed. The problems with identification and taxonomy of soft-bodied hexacorals were summarized, analysed and discussed. A working protocol was proposed as a new standard. An illustrated identification guide, which includes all known species, was made for the better known Mediterranean soft-bodied hexacorals. \nThe crisis in systematics of soft-bodied hexacorals may be overcome by consequent ap-plication of modern methods and the close cooperation of taxonomists, ecologists and mo-lecular biologists. New funding programs and a growing interest within the younger genera-tion give cause for the hope that soft-bodied hexacorals might receive the attention merited by their ecological importance in marine benthic communities.