One hundred and nine dogs were diagnosed as having been poisoned by viper (Vipera xanthina palestinae) venom between 1989 and 1996. Most of the cases occurred between April and September (86.2 per cent), with peaks in May (25.7 per cent) and July (20.2 per cent), and very few between November and February (3.6 per cent). Forty-two per cent of the dogs were poisoned in the evening (18.00 to 22.00), with a relative risk of 6.85, 17.4 per cent between 22.00 and 02.00, and 16.5 per cent between 14.00 and 18.00. The median age of the dogs was three years, and almost 80 per cent of them were from rural households. German shepherd dogs and rottweilers were over-represented (relative risk 1.98 and 1.87 respectively), and mongrel dogs and pinschers were under-represented (relative risk 0.41 and 0.53 respectively). Fifty-six per cent of the bites were on the head (excluding the mouth, lips and pinnae), 16.5 per cent on the front limbs, 9.7 per cent on the mouth and lips, 8 per cent on the hindlimbs, 4.4 per cent were submandibular and 5.4 per cent were at other sites. The main clinical signs were local swelling (98.2 per cent) and oedema (94.5 per cent), panting (45.7 per cent), tachypnoea (42.5 per cent), pain (34.9 per cent), tachycardia (29.8 per cent), lameness (25.7 per cent), and lymphadenomegaly (23.9 per cent). The mortality rate was 3.7 per cent. The most common haematological abnormalities were neutrophilia (67.6 per cent), leucocytosis (54.9 per cent), thrombocytopenia (51.9 per cent), increased haematocrit (47.6 per cent), and a left shift of neutrophils (37.8 per cent). Many biochemical abnormalities were observed, of which the most common were high activities of lactate dehydrogenase (84.6 per cent), creatine kinase (69 per cent), gamma-glutamyltransferase (40 per cent) and aspartate aminotransferase and high concentrations of globulin, phosphate and total bilirubin (33.3 per cent in each case).