The toxic actions of aminophylline manifest themselves in three categories; first, excessive stimulation of the central nervous system; second, gastric irritation resulting in severe vomiting, and third, effects on the kidney. Six cases have been presented demonstrating all of these toxic manifestations. It is believed that alertness to these signs and symptoms in the future will prove aminophylline poisoning to be a relatively common, often serious problem. In the practise of pediatrics more caution should be exercised in using aminophylline, especially with regard to dosage.