PBC is a cholestatic liver disease of unknown etiology with autoimmune features that is often associated with other autoimmune diseases. We analyzed peripheral blood T-cell subsets in patients groups with PBC (n = 11), non-PBC hepatobiliary disease (n = 11) and an age and sex matched control group (n = 11) by two color FACS-analysis. Seven out of eleven PBC patients exhibited markedly lowered and nearly undetectable levels of y8 T-cells (<0.8%). None of the individuals in the non-PBC hepatobiliary disease (HBD) gkroup or the normal control group had y8 values below 1%. The other four individuals in the PBC group hadγδvalues within the normal range. Overall, the PBC group had a statistically significant, lowered mean percentage ofγδT-cells (L.50%) as compared to the hepatobiliary disease group (3.76%) and the control group (4.22%, p = 0.01). The percentages of CD4+and CD8+andαβTCR+CD4-CD8−double negative cells in PBC patients did not differ from the control group. PBC patients with normalγδcell counts did not differ from the PBC group with lowγδvalues in autoantibody titers, liver tests or treatment of the disease. As a possible cause for the observed decrease ofγδT-cells three sera of PBC patients with low y8 T-cell counts were screened by single color, indirect immunofluorescence for antibodies toγδT-cell enriched lymphocytes, but no differences to control sera were observed. In conclusion, we describe what appears to be a disease-specific but inexplicable marked decrease inγδT-cells in the peripheral blood of a group of patients with PBC. The possible role of aγδ-specifjc superantigen in the pathogenesis of the disease is discussed.