Some basic scientific data suggest that (S)-enantiomers of beta(2)-agonists have different and sometimes opposing effects to (R)-enantiomers. These data may explain the paradoxical response of the airways to the repeated, chronic administration of racemic beta(2)-agonists. Therefore, it is possible that the use of (R)-enantiomers of beta(2)-agonists may be an alternative option to reduce the risks of long-term administration of inhaled long-acting agents. Arformoterol is the (R,R)-enantiomer of formoterol. It is currently available for use as a nebulized solution of arformoterol tartrate and is approved in the USA for twice-daily administration in patients with chronic obstructive pulmonary disease (COPD). Clinical trials in COPD patients have demonstrated that arformoterol is as effective in improving lung function and symptoms as other available long-acting inhaled beta(2)-agonists. Moreover, its safety for long-term administration has been documented in this population. These findings indicate that arformoterol is an effective option for patients with COPD who could benefit from sustained bronchodilation delivered through nebulization, and can be an alternative for patients who cannot use conventional inhaler devices, including metered-dose inhalers or dry-powder devices.