On the base of literature data, field investigations, studies of herbarium collections and plants in culture, the authors summarize the taxonomic, phytogeographical, karyological and palynological knowledge of certain species of the genus Arum. Special attention is addressed to Arum cylindraceum s.l. (that is with A. alpinum, A. lucanum, A. intermedium and A. maculatum subsp. danicum included). Some comments are also given about A. apulum and A. idaeum. The misinterpretation of many species were mostly caused by old and incomplete first diagnoses, lack of type specimens and locus classiCUS, complicated by a large variability which is linked partly with hybridization.