1. Respiratory and cardiovascular failure are principle toxic effects of beta-blocker overdose. Respiratory arrest is the primary cause of death in beta-blocker intoxicated rats. 2. The effect of beta-adrenoceptor agonists on respiratory and cardiovascular failure in beta-blocker overdose was investigated in a model of acute d,l-propranolol (30 mg kg-1 h-1) intoxication in spontaneously breathing rats. 3. Neither the aselective, hydrophilic beta-agonist isoprenaline (10, 25, 50 micrograms kg-1 min-1), nor the beta 1-selective, lipophilic beta-agonist flerobuterol (1, 3, 10 microgram kg-1 min-1) and the beta 2-selective, lipophilic beta-agonist clenbuterol (10, 25, 50 micrograms kg-1 min-1) had any beneficial effect on cardiovascular and respiratory variables or survival time in d,l-propranolol intoxicated spontaneously breathing rats. 4. Isoprenaline (10 micrograms kg-1 min-1) had no favourable effect on haemodynamic and respiratory variables in artificially ventilated d,l-propranolol intoxicated rats either. 5. Addition of dopamine to isoprenaline resulted in a significant reduction of survival time, primarily caused by a decreased in mean arterial blood pressure, in artificially ventilated d,l-propranolol intoxicated rats. Addition of glucagon to isoprenaline did not affect survival time. 6. Artificial ventilation is the most important supportive measure in d,l-propranolol intoxication in the rat.