We present a case of acute lithium ion intoxication in which the main clinical feature was respiratory failure secondary to pulmonary oedema possibly due to myocardial depression, associated with profound stupor. The initial lithium ion concentrations were 3.15 mmol/l in plasma and 27.6 mmol/l in urine. Under symptomatic treatment with oxygen, digitalis and diuretics, both the pulmonary and the neurological disorders reverted gradually, in parallel with the decreasing plasma lithium ion concentrations.