Concentrations of dioxins (PCDD) and dibenzofurans (PCDF) were analysed in adipose tissue from seven patients with malignant lymphoproliferative diseases and 12 surgical patients without a malignant disease. All cases in the first group had reported potential exposure to PCDD and PCDF. Of the analysed congeners significantly higher concentrations of 1,2,3,7,8-pentachlorodioxin, 1,2,3,6,7,8-hexachlorodioxin, and 2,3,4,7,8-pentachlorodibenzofuran were found in the cases with lymphoproliferative diseases compared with the patients in the other group. Higher mean concentration of 2,3,7,8-TCDD was also found in the first group but not significantly so. Toxic equivalents of PCDD and PCDF were significantly higher in the first group (mean 64.7 pg/g, range 19.9-187) than in the second group (mean 29.7 pg/g, range 12.9-53.4). Even if the cases with lymphoproliferative diseases in this case series were potentially exposed to PCDD/PCDF in contrast to the other group, the observed differences may be of may be of interest in relation to the aetiology of these malignancies. Immunosuppression increases the risk for malignant lymphoproliferative diseases, and PCDD/PCDF have established immunotoxic properties.