Breathlessness is an extremely common symptom. Its genesis is incompletely understood but is known to be largely determined by many of the mechanical factors associated with the act of breathing. As with all subjective sensations various other factors including volition, behavioural style and other cortical and subcortical factors play a part in its genesis. The relief of breathlessness is primarily directed at the underlying disorder. In those conditions and situations where specific therapy has little to offer or little impact it is reasonable to consider ways of reducing the perception of breathlessness by pharmacological means. However, to date there is no convincing evidence that use of drugs in the pursuit of the relief of breathlessness has any specific effect in modifying the perception of this often distressing symptom. Any reduction in breathlessness achieved in this way can be adequately explained in terms of a reduction in ventilation and other indices of respiratory mechanics.