To date there have been seven published randomised controlled trials of the Buteyko method.  All the trials have shown either significant reductions in the need for medication or improvements in asthma control.  There are no known negative trials.

In a trial conducted in Canada (Cowie et al., 2008), 129 patients with asthma were randomised to receive breathing exercises from either a Buteyko practitioner or a chest physiotherapist.  In the Buteyko group the proportion of patients achieving good control of their asthma increased from 40% at baseline to 79% at six months.  Though the control group also experienced improvements in asthma control, in the Buteyko group this improvement was associated with a statistically significant reduction in the average dose of inhaled steroid.  In other Buteyko trials (Bowler et al.,1998; Cooper et al., 2003; McHugh et al., 2003; Slader et al., 2006) the need for reliever medications was reduced by an average of 80-90%.

For a more detailed survey of clinical trials on Buteyko, see my presentation to the Primary Health Care Group at Middlesex University, Asthma Management with Buteyko Breathing Therapy.