Patients with bronchiectasis suffer from sputum production, recurrent exacerbations, and progressive airway destruction. Erythromycin is effective in diffuse panbronchiolitis, another suppurative airway disorder, although its efficacy is unknown in idiopathic bronchiectasis. A double-blind placebo-controlled study was therefore conducted to evaluate the effects of 8-week administration of low dose erythromycin (500 mg b.i.d.) in steady-state idiopathic bronchiectasis. Patients in the erythromycin group (n=11, 8 female, mean age 50+/-15 yrs), but not the placebo group (n=10, 8 female, mean age 59+/-16 yrs) had significantly improved forced expiratory volume in one second, forced vital capacity and 24-h sputum volume after 8 weeks (p<0.05). There was no parallel improvement in sputum pathogens, leukocytes, interleukin (IL)-1alpha and IL-8, tumour necrosis factor-alpha, or leukotriene B4. The results of this pilot study show that low-dose erythromycin improves lung function and sputum volume in bronchiectasis. Further studies are indicated to evaluate the efficacy of long-term erythromycin therapy in bronchiectasis.