Tobacco smoke is the crucial factor at the beginning and in the course of the bronchial inflammation leading to COPD. It has been shown that cigarette smoke in vitro leads to a MAP kinase and NF-κB-dependent increase of pro-inflammatory cytokines, and inhibits bacteria-induced expression of β-defensins. Several studies revealed an increase of inflammatory cytokines like IL-8 and TNF in the sputum of smokers. Further studies demonstrated an up regulation of LTB4 and LBP possibly due to the LPS derived from tobacco smoke. Hasday et al could show that up to 15 ng per cigarette LPS is released. In principle, the cigarette smoke exposure liked a mild LPS inhalation. In separate work, we could show that LPS inhalation in healthy non-smokers to an increase of CRP and LBP concentrations in the serum lead. In another study of adolescents, 24 smokers (age 17.7 years) and 24 non-smoking (age 17.5 years) were compared. The CO in smokers was significantly increased, and the NO concentrations decreased. At the same time there was a significantly greater bronchial hyperreagibility in the smoker group.