The correlation between blood PCB concentration and clinical manifestation of symptoms was investigated in 259 chronic "Yusho" patients, using the information obtained from the nationwide health examination conducted in 1988, twenty years after the outbreak. Concentrations of blood PCBs ranged 0.6-32.0 ppb (mean; 4.78), and they were categorized into approximate quartile for analysis. For general fatigue, odds ratios at 2.7+, 4.1+, and 6.1+ ppb were 2.4, 3.6, and 3.1, respectively, with a reference category of < 2.7 ppb (test for trend; p < 0.005). For numbness in extremities, the corresponding odds ratios were 2.8, 2.8, and 2.9(p < 0.005). For comedone, they were 1.4, 1.0, and 4.0 on face (p < 0.025); and 3.6, 4.6, and 9.5 on trunk (p < 0.005), respectively. A distinctive increase in odds ratio was observed at 2.7 ppb for these two subjective symptoms; and at 6.1 ppb for skin symptoms. The blood PCB concentrations among patients were relatively close to the normal subjects. Therefore, the observed correlations may be due to the effects of PCBs with a peculiar pattern in components, PCQs or PCDFs, taken and retained in the patients. Association with blood PCBs was also suggested for headaches; abnormal breath sounds; and acneiform eruptions in the genital region, but were statistically insignificant. None of the eye symptoms showed significant association with blood PCBs.