Increasingly persuasive evidence implicates adenosine in the pathophysiology of asthma. Adenosine exerts its manifold biological activities by interacting with at least four adenosine receptor subtypes. Selective activation or blockade of these sites is being exploited by the pharmaceutical industry in an attempt to generate novel therapies for asthma. Compounds have been designed which downregulate the A1 receptor, activate the A2A receptor or block the A2B receptor and are currently in development for this condition.