The safety of the most widely prescribed antiasthma drugs, beta 2-adrenoceptor agonists, has recently been questioned. Issues such as their suitability for long-term and regular prophylactic use are addressed in this Comment article by Peter Barnes and Fan Chung, who examine the possibility that the beta 2-agonists themselves contribute to worsening symptoms in asthma patients, thus setting up a vicious circle with greater use of the drugs. They conclude that it would be prudent to restrict the use of beta 2-agonists in asthma to on-demand immediate symptom control.