We have assessed a new positive expiratory pressure device, the Flutter VRP1, in 20 patients with moderately severe asthma. Patients were studied for an initial 1-week 'run-in' period, followed by 2 weeks of the flutter device in one of which the ball-bearing was removed from the bowl. Peak expiratory flow rates, salbutamol inhaler requirements and visual analogue scores were recorded daily. Ease of sputum expectoration showed a significant improvement after 6 days of the flutter device, but there were no differences in objective measurements of lung function nor in salbutamol use. The device may be a useful adjunct to asthma therapy.