Background: Lipid peroxide (LPO) in comedones, which are produced as a result of sebum oxidation, might potentially induce interleukin-1α (IL-1α) and exacerbate comedogenesis and inflammatory changes in comedones. Objective: To investigate the relationship of proinflammatory cytokines and LPO levels in the extracts of comedones with the acne of clinical difference between smokers and non-smokers, and with the severity and distribution of the acne lesions. Methods: Twenty-two non-smoking and 21 smoking adult acne patients were evaluated by comedone extraction and measurement of proinflammatory cytokines and LPO levels. Acne severity and distribution of the lesions were also analyzed. Results: Relative to the non-smoking group, smokers had significantly higher levels of IL-1α and LPO in comedones. Their levels showed a positive correlation. However, there were no statistically significant difference between the severity or distribution of the disease and the levels of LPO and IL-1α in comedones. Conclusion: Smoking may be involved in the pathogenesis of adult acne by increasing the oxidative stress that results in subsequent accumulation of LPO in comedones. (Ann Dermatol 26(1) 11∼ 16, 2014)