Fertil Steril. 2009 Apr 24; Cupisti S, Häberle L, Dittrich R, Oppelt PG, Reissmann C, Kronawitter D, Beckmann MW, Mueller AOBJECTIVE: To evaluate the impact of smoking on endocrine, metabolic, and clinical parameters in women with polycystic ovary syndrome (PCOS). DESIGN: Cohort analysis. SETTING: University hospital. PATIENT(S): 346 women with PCOS, including 98 smokers and 248 nonsmokers. INTERVENTION(S): Screening panel, including physical examination, weight and height measurement, and ultrasound examination of the ovaries, and hormone and insulin measurements. MAIN OUTCOME MEASURE(S): Clinical, metabolic, and endocrine parameters, oral glucose tolerance test, calculation of insulin resistance indexes. RESULT(S): In women with PCOS, smoking was associated with statistically significantly increased levels of fasting insulin and calculated free testosterone (cFT) and with a raised free androgen index (FAI) score, which resulted in aggravated scores on the homeostatic model for assessment of insulin resistance (HOMA-IR). However, no differences were observed between the smoking and nonsmoking groups with regard to the clinical parameters for hirsutism, acne, ovulatory function (classified as eumenorrhea, oligomenorrhea, and amenorrhea), or polycystic ovaries using the ultrasound criteria recommended according to the Rotterdam definition. CONCLUSION(S): In women with PCOS, smoking is associated with increased free testosterone and fasting insulin levels, resulting in aggravated insulin resistance. However, there were no differences between smokers and nonsmokers when clinical parameters were compared.