The abdominal subcutaneous adipose tissues, the mother milk, and the blood samples of yusho patients were collected between 1986 and 1988, and analyzed for polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) by high resolution gas chromatography/high resolution mass spectrometry in selected ion monitoring mode. PCDDs and PCDFs were found all of the samples examined.: 1,2,3,7,8-Pentachlorodibenzo-p-dioxin (pentaCDD), 1,2,3,6,7,8-hexaCDD, octaCDD, 2,3,4,7,8-pentachlorodibenzofuran (pentaCDF), and 1,2,3,4,7,8- and 1,2,3,6,7,8-hexaCDF were detected. The levels of PCDDs was several times lower than those of PCDFs in all samples. The concentrations of PCDDs and PCDFs found in the fat of the mother milk were similar to those of the adipose tissues. On the other hand, the levels of PCDDs and PCDFs in the blood samples were several hundred times less than those of the adipose tissues.