We measured the cotinine levels in urine and serum of academic staff members and performed a questionnaire survey on smoking and passive smoking to assess the association of cotinine levels and the current status of self-reported passive smoking. We enrolled 506 subjects including current smokers (n=25). Cotinine levels in urine showed significant correlation with those in serum (p<0.001). Most of the subjects (71.1%) answered that they were not exposed to passive smoking based on the survey; however, 20.6% of them were found to be exposed to passive smoking assessed by urinary cotinine level. The questionnaire also revealed that 23.4% of the subjects showed an increase in urinary cotinine levels; however, 62.7% of them were not aware of passive smoking. The concordance rate of self-reported exposure to passive smoking and assessment of passive smoking by urinary cotinine levels was only 65.2%. In summary, a measurement of urinary cotinine levels might be useful for the assessment of passive smoking and prevention of smoking-related disorders.