Abstract: The determination of serum AchrA in patients with SLE （43） or other rheumatic diseases （ODRs, 109） and in normal individuals （42） was done by indirect immunofluorescence assay （ⅡF）, using the polytene chromosomes of the third instar larve of Drosophila melanogaster as the substrate. The results showed that the serum AchrA was negative in all of the 42 normal individuals and the 109 patients with ORDS and the it was positive in 19 （44%） of the patients with SLE. Active SLE was found in 16 patients （84%） in the 19 AchrA positive group and 13 （54%） in the 24 AchrA negative group. The incidence of arthritis/arthralgia, photosensitivity, glomerulanephritis and anemia in the SLE patients were higher in AchrA positive group than that in AchrA negatie group. In contrast, patients with nephrotic syndrome were more common in AchrA negative group than in AchrA positive group. It is suggested that serum AchrA is auite specific and sensitive for SLE and that the finding of positive AchrA is clearly associated with activity of SLE and renal involvement.