Serious neurological symptoms are common in patients with a serum sodium concentration below 115 mmol l-1. The treatment is controversial and the most adequate rate of sodium correction to avoid both morbidity due to residual hypo-osmolality and therapy-induced neurological sequelae is debated. The management of symptomatic hyponatraemia is discussed here against the background of two cases and a literature review. It is concluded that the treatment should be based on whether the electrolyte disturbance is acute (< 24-36 h) or has developed insidiously. Slow sodium correction (< 0.5 mmol l-1 h-1) in patients with chronic hyponatraemia and rapid correction (1-2 mmol l-1 h-1) to a moderately hyponatraemic level in those with an acute development are recommended. If available data do not permit differentiation between the two conditions in a patient with seizures or in coma, rapid correction with sodium chloride and furosemide for 3-4 h followed by slow correction therapy is suggested.