Twelve adult asthmatic patients participated in an open, randomized, cross-over comparison between cumulatively increasing doses of terbutaline sulphate administered via the multiple dose powder inhaler (Turbuhaler) or via a pressurized inhaler. Turbuhaler and the pressurized inhaler showed equipotency both with respect to bronchodilatation and side effects. Both treatments produced a significant increase in pulmonary function measurements, forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). No increase in pulse rate was seen with either treatment but there was an increase in tremor at higher doses with both treatments. Inhalation of beta-agonists via Turbuhaler seems to be an effective way of treating asthma.