Chapter 1. In Europe, V. berus is extensively distributed and causes more bites than any other species within the genus Vipera. In Hungary, envenoming by the native V. berus is relatively rare compared to other European countries, although, certain cases may have more serious consequences than usual and leading unique and challenging medical emergency situation mainly due to the possible geographical venom variations. In this chapter, we provide here a review and discussed the main epidemiological aspects and significance of incidents inflicted by V. berus in Hungary: 1) Epidemiological aspects of Vipera berus envenomings in Hungary, and 2) Envenomings that published in the Hungarian literature – Brief review.   Chapter 2. Envenomings by V. berus result in characteristic systemic symptoms including early ‘anaphylactic’ features (i.e. tachycardia, gastrointestinal symptoms), dizziness, hypotension, shock, coagulopathy and neutrophil leucocytosis. These symptoms resemble those caused by V. aspis, reflecting the similarities in the composition of their venoms. Systemic neurotoxicity has been described in patients envenomed by certain populations of some subspecies of V. aspis and V. ammodytes in Europe. It has been attributed to pre-synaptic (ammodytoxins) or post-synaptic neurotoxic phospholipases A2 in their venoms. However, neurotoxicity is the most unusual and unexpected clinical feature of V. berus envenoming. This chapter demonstrates two clinical reports from eastern Hungary with other interesting features and review the scanty and somewhat obscure literature on this phenomenon: entitled as Case reports from eastern Hungary; Case report 1, Case report 2. Chapter 3. Since intraspecific venom variability of the taxon may also have important clinical implications, the third aim of the dissertation was to demonstrate experimentally and biochemically the venom individualities of a given population of V. b. berus in eastern Hungary. We studied the individual venom variability in this Hungarian adder population by: 1) Comparison of the electrophoretic protein pattern of venom samples, 2) Analysis of the phospholipase A2 (PLA2) content of venoms by MALDI-TOF-MS, 3) Phospholipase A2 (PLA2) activity assay, 4) Protease assay, 5) Determination of murine LD50 of the crude venoms and effects on chicks in vivo, 6) Neuromuscular effects of venom on frog nerve-muscle (FNM) preparation, 7) Neuromuscular effects of venom on chick biventer cervicis (CBC) preparation, and 8) Inhibitory venom effect on a glutamergic synapse of the rat brainstem slice preparation. This chapter may help to better understand the nature of their venom complexity based on our results and the symptoms-manifestation on envenomed humans, and eventually their evolutionary and taxonomic aspects, as well.