Two breath-actuated inhalers, the Turbohaler and the Rotahaler, were compared in 24 patients with chronic asthma using an open, cross-over study design. Patients were treated with terbutaline (500 micrograms) and salbutamol (400 micrograms) four times daily, each trial period lasting three weeks. Mean morning peak expiratory flow (PEF) values were higher during Turbohaler treatment, but were similar 15 min after inhaler use. The Turbohaler was found to be easier to use than the Rotahaler.