To investigate biomarker-based exposure to phthalates and related factors with demographics, 100 subjects who had participated in comprehensive health check-up were selected. We collected demographics through questionnaires and analyzed urine samples for 5 phthalates. Statistical likelihoods and regression methods were applied for data analysis using censored data. The highest levels of urine phthalates were 216$mu extrm{g}$/ml in di-isodecyl phthalate, 29.0$mu extrm{g}$/ml in di-butyl phthalate, 5.78$mu extrm{g}$/ml in di-(2-ethylhexyl) phthalate. The median values of di-(2-ethylhexyl) phthalate were 0.2340 $mu extrm{g}$/ml for male smokers, 0.0399 $mu extrm{g}$/ml for male non-smokers and 0.0085 $mu extrm{g}$/ml for female non-smokers, respectively. Di-(2-ethylhexyl) phthalate, benzyl butyl phthalate and di-isodecyl phthalate were higher in males than in females. In addition, mono-2-ethylhexyl phthalate was decreased with age. Our findings suggest that there might be significant demographic variations in exposure and/or metabolism of phthalates, and that health-risk assessment for phthalate exposure in humans should consider different potential risk groups.