Common krait (Bungarus caeruleus) is the deadliest snake found commonly in the dry zone of Sri Lanka. In Anuradhapura, 210 farmers bitten by the common krait over a three year period were investigated prospectively from 1 January 1996. The sex ratio was equal, 110 (52%) patients were in the age group 10-30 years. One hundred and one (48%) patients were severely envenomed and needed mechanical ventilation from 12 hours to 29 days (mode two days). The bite occurred at night while the victims were asleep on the floor. In 99 (47%) situations killed specimens were available for identification. The cardinal symptom was abdominal pain developing within hours of the bite. Alteration in the level of consciousness was observed in 150 (71%) patients: drowsy in 91 (43%), semiconscious in 24 (11%), and deep coma in 35 (17%). Autonomic disturbances included transient hypertension, tachycardia, lacrimation, sweating, and salivation. These manifested in 139 (66%) patients with moderate to severe envenomation. One hundred and forty nine (71%) had hypokalaemia and 105 (50%) metabolic acidosis, anterograde memory loss in 84 (40%), and delayed neuropathy in 38 (22%) patients. Polyvalent antivenom had no significant benefit (t = 0.5) in reversing respiratory paralysis and preventing delayed neurological complications. Sixteen (7.6%) patients died and a submucosal haemorrhage in the stomach was seen at necropsy in three cases. Mortality could be minimised with early and free access to mechanical ventilation.