The efficacy of ipratropium and salbutamol was determined in 117 patients with acute asthma who presented to an emergency department to determine whether the order of administration of the two agents affects the improvement in peak flow rates. Patients were given two nebulized treatments at an interval of one hour in a randomized, double-blind design. They received either 5 mg nebulized salbutamol followed by 0.5 mg ipratropium, ipratropium followed by salbutamol, or both drugs administered together followed by nebulized saline. Ipratropium was an effective bronchodilator when given as the first agent. Simultaneous administration with salbutamol was as effective as sequential administration. At one hour after treatment, there was no difference in peak flow between the combination of drugs and either drug given alone. Ipratropium given after salbutamol was not superior to saline solution given after the combination of drugs. Our data do not suggest a substantial therapeutic effect from addition of ipratropium to salbutamol in the immediate treatment of acute asthma.