Venoms from five of the nine poisonous Vipera species found in Europe (V.berus, V.ammodytes, V.aspis, V.xanthina and V.lebetina) were assessed for their physical characteristics and for enzymatic (phospholipase All proteolytic and hyaluronidase) and biological activities (haemolysis, platelet aggregation, neurotoxicity and myotoxicity). Antivenoms were raised in sheep against these venoms, using a low dosage immunisation schedule. The immunoglobulins were partially purified by sodium sulphate precipitation, cleaved with the plant protease papain to produce Fab and finally affinity purified to collect only those Fab directed specifically against venom components. The different antivenom fractions Were characterised and assessed for their ability to neutralise the enzymatic and biological activities of the venoms as well as to provide in vivo protection in mice. Fab Was equally efficient in EDso compared to the IgG, but was not as efficient as F(ab)2 in some enzyme assays, or as efficient as the IgG in inhibiting myotoxicity and neurotoxicity. Cross-reactivity studies showed that these venoms are of similar composition and that the ovine antivenoms contained antibody populations directed against most of their components. As one aim was to produce more efficient antivenoms, the ovine F(ab)2 antibody fragment raised against V.a.ammodytes venom was compared with the currently available commercial antivenoms, produced by hyperimmunising horses. Finally, immunoenzymometric assays and radioimmunoassays were developed and validated for V.b.berus and V.a.ammodytes venoms and applied to measuring venom levels in blood and urine in envenomated patients. Antivenom concentrations in clinical samples were measured by immunoenzymometric assays.