A national survey of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) in emission gases from the municipal waste incinerators in 1997 revealed that the Nose Bika Center was heavily contaminated by PCDF. Ninety-four workers underwent a physical examination, and blood biochemistry, lymphocyte marker, and NK activity studies were carried out, along with blood dioxin measurements. Information on working history, life-style, and dietary habits was obtained by questionnaire and interview. The blood dioxin levels were as follows. The median TEQ of dioxins was 39.7 pg I-TEQ/g lipid, and the range was 13.3 to 805.8. The median 2,3,7,8-TCDD concentration was 3.9 pg TEQ/g lipid, and the range was <1 pg TEQ/g lipid (one case) to 13.4 pg TEQ/g lipid. The median TEQ of coplanar PCB was 10.8 pg I-TEQ/g lipid, and the range was 3.1 to 54.2 pg TEQ/g lipid. The congener-specific distribution was quite similar to that in soil around incinerator and waste in the factory. The relationship between dioxin concentrations and work history in the factory showed that the fluidized incinerator and fly ash treatment areas were high-risk work areas. Correlation analyses between body burden, PCDD/PCDF TEQ, Co-PCB TEQ and various laboratory data showed significant positive correlations between dioxin levels and GGT, total protein, uric acid and calcium, and a negative correlation with Fe. However, these correlations disappeared as a result of multivariate analysis adjusted for age, smoking status, and alcohol drinking. Increased NK activity and lower response to PHA stimulation remained significant even after adjusting for age. History of hyperlipidemia and allergy had significantly increased odds ratios. A study on the risk to other workers in the same type of incinerators is under way. Health effects of chronic exposure mainly to PCDF will be clarified by follow-up.