Despite the trend towards newer therapeutic agents, theophylline continues to play a major role in the treatment of reversible airway obstruction. Clinical use of the drug is complicated by a relatively narrow therapeutic range and a large pharmacokinetic variability between patients. Generally, however, theophylline toxicity is foreseeable and preventable. Most cases can be attributed to either inadvertent or intentional overdosing of the drug. Age, disease state and drug interactions are other factors which may contribute to its toxicity. Nausea, vomiting and tachycardia are common signs of mild theophylline toxicity; seizures, ventricular arrhythmias and hypotension are life-threatening manifestations of severe toxicity which may respond poorly to standard therapy. Although serum theophylline concentration correlates with toxicity in a general fashion, life-threatening adverse reactions are not readily predictable from the drug concentration alone. Treatment of theophylline toxicity primarily involves supportive care along with gastric lavage and administration of activated charcoal to facilitate drug removal. The early use of haemoperfusion may be life-saving in cases of severe toxicity.