The polychlorinated quaterphenyl (PCQ) concentrations in the blood are important discriminative parameters in Yusho patients. The blood samples of 81 persons were analyzed for PCQ in the 2005 annual inspection for Kanemi rice oil poisoning. PCQ was detected in 28 blood samples (ranging from 0.02 to 4.05 ppb). The means of PCQ concentration in the blood were 1.80 ppb (0.33-4.05 ppb) in pattern A, 0.71 ppb (<0.02-2.26 ppb) in pattern B, 0.03 ppb (< 0. 02-0.14 ppb) in pattern BC and 0.02 ppb (<0.02-0.45 ppb) in pattern C, respectively. PCQ was still present at high concentration in the blood of patterns A and B. Since PCQ concentration is a useful diagnostic criteria, it is important to follow up on this survey of blood PCQ levels.