We investigated the levels of polychlorinated dibenzo-p-dioxins (PCDDs) and their related compounds in blood and sebum from Yusho and Yu-Cheng patients and findings compared with those of normal subjects. Concentrations of these compounds in blood and sebum still were obviously reflected the chemical concentration in the causal rice oil ingested 17 or 26 years since the outbreak. In addition, sebum form the body surface was the most useful sample for monitoring the amount of chemicals contaminating the human body.