Flow cytometric 2-color analysis of peripheral blood lymphocytes from patients with systemic lupus erythematosus (SLE) showed a reduction of relative and absolute number of CD4+ CD29+ cells compared to matched healthy individuals. This abnormality was more marked in patients with active/very active disease. Absolute number of CD4+ CD29+ cells was negatively correlated with spontaneous anti-DNA Ig production that we demonstrated to be a laboratory index strongly correlated with a clinical disease activity score. A decrease of the percentage of CD8+ CD29+ lymphocytes in patients with active disease was also observed.