Recent advances in chronic obstructive pulmonary disease (COPD) treatment offer symptom relief, but disease modification remains an unmet goal of pharmacotherapy. Reducing the frequency and severity of COPD exacerbations may help slow disease progression and reduce the morbidity, mortality, and costs associated with these major events. Other desirable characteristics for a COPD treatment include a once-daily dosing schedule, an oral formulation, and a low frequency of systemic side effects. Phosphodiesterase 4 inhibitors have been in clinical development for some years and roflumilast is currently the most advanced of these agents. In this review, the preclinical evidence, clinical safety, and efficacy of roflumilast available in published reports are considered. The data reviewed here suggest that the clinical efficacy of roflumilast occurs through a mechanism unrelated to bronchodilation and may be due to the suppression of lung inflammation. Lung function improved with roflumilast treatment and in some studies, the reduction in exacerbations was substantial and statistically significant. Notably, this effect appeared to be greatest in the subgroup of patients with more severe disease and more severe exacerbations. The evaluation of roflumilast safety largely centers on gastrointestinal adverse events, with diarrhea, nausea, and weight loss occurring more frequently with the drug than placebo. If approved for general use, we expect roflumilast to find its role initially as a substitute for inhaled corticosteroids in the maintenance treatment of severe and very severe disease, particularly in patients who have frequent acute exacerbations, and perhaps as a supplementary drug when symptoms are not adequately controlled by current conventional COPD therapy.