To evaluate the effects of passive smoking identified by urine cotinine on serum carotenoids and alpha-tocopherol, we categorized 124 residents in a rural city of Japan into 4 groups by their urine cotinine/creatinine (Cot/Cr) ratio (u.d. (undetectable); low (0-50 ng/mg); moderate (50-120 ng/mg); high (> 120 ng/mg)) and compared the serum carotenoids and alpha-tocopherol levels among these groups. We identified passive smoking by low Cot/Cr ratio level. After controlling on related factors, men with low Cot/Cr ratio showed significantly lower serum zeaxanthin/lutein levels than men with u.d. Cot/Cr ratio. The difference was still marginally significant after excluding self-reported current smokers from the low Cot/Cr group. It is suggested that low level exposure to tobacco smoke, which has been reported to be equivalent to that for passive smokers, could be associated with decreased serum zeaxanthin/lutein levels in men.