Clinical findings on admission to hospital and outcome in 295 consecutive patients with severe tricyclic antidepressant self-poisoning treated in an ICU are presented. Cerebral depression was observed in 92%, convulsions in 23% and respiratory failure was present in 72%. Cardiovascular function was impaired in 44% and an abnormal ECG was found in 57%. Cardiac arrest was treated in 14 patients (6%) of whom seven were resuscitated. The mortality rate was 2%. All patients were artificially ventilated. A beneficial effect of respiratory alkalosis on cardiac arrhythmias is supported.