There is a major burden from asthma in New Zealand, including severe attacks, with over 6,000 hospital admissions due to asthma annually. Surprisingly the optimal regimen for the management of severe asthma attacks has not been established, particularly in relation to the dosing regimen for the bronchodilator salbutamol. This has led to a wide variation in recommended salbutamol regimens through emergency departments in New Zealand. In two randomised controlled trials we aim to compare the efficacy and safety of 'low' and 'high' salbutamol regimens in common use in New Zealand emergency departments in the treatment of moderate and severe attacks of asthma in adults presenting to the Wellington Hospital Emergency Department. The results should determine the preferred salbutamol regimen in acute attacks of asthma in adults.