To test the value of decreased peripheral leuko-/lymphocytes as screening test for the diagnosis lupus erythematosus (LE). Laboratory routine analyses, and flow cytometry (CD3, CD4, CD8) have been performed in 124 LE-patients. Other subjects included 57 healthy controls, 130 patients with non-autoimmune inflammatory diseases (dermatitis, psoriasis), and 17 patients with another autoimmune disease (progressive systemic sclerosis [PSS]). Numbers of peripheral blood leukocytes (P<0.0005), lymphocytes (P<0.00002), CD3+, and CD3+ CD4+ cells from LE-patients were significantly lower than from controls, patients either with dermatitis, psoriasis or PSS. CD3+ CD8+ cells were significantly diminished in patients with LE and PSS. Decreased numbers of white blood cells, lymphocytes and some of their subsets seem to indicate LE. Patients with PSS only had decreased T-cytotoxic cells. Inflammatory dermatoses lacking the autoimmunity as background have normal cell counts. For screening purpose absolute values of the mentioned blood cell subsets seem to be useful to distinguish both autoimmunity from non-autoimmune inflammatory diseases, and LE from PSS.