Chronic bronchitis is a lifelong disease with significant effects on the patient and on the costs to health insurance institutions. Acute exacerbations in chronic bronchitic patients may have a negative impact on patients' quality of life and on the progression of the disease, particularly in more severe patients. The clinical efficacy of the immunoactive bacterial extract OM-85 BV has been shown in several clinical trials, a cost-effectiveness evaluation (CEA) of its use in chronic bronchitic patients has not been fulfilled so far. In this study a meta-analysis on the preventive treatment of acute exacerbations with OM-85 BV and a CEA, focusing on direct costs only, was performed. The meta-analysis showed a mean value of 0.6 prevented acute exacerbations per 6 months per patient, and a reduction of 9 days in antibiotic treatment per 6 months per patient. CEA evaluated the different cost elements. The mean direct cost (consultations, antibiotics, etc.) for the treatment of 1 acute exacerbation in chronic bronchitic patients was calculated as 143, 459 Lira. Thus for 0.6 prevented acute exacerbations per 6 months per patient a reduction in cost of 86,075 Lira (0.6-143,459) could be expected. The additional costs for the preventive treatment with OM-85 BV, based on prices for Italy, are 34,980 Lira per patient per 6 months. In conclusion, the effective cost savings per patient per 6 months are 51, 095 Lira. The sensitivity analysis revealed only one critical parameter, i.e. the clinical effectiveness of OM-85 BV. Even assuming 0.3 prevented exacerbations per 6 months per patient, the preventive treatment still proved to be cost effective.