SUMMARY In clinically quiescent SLE hypergammaglobulinaemia, presence of autoantibodies, and increased soluble IL‐2 receptors (sIL‐2R) have been reported, suggesting persistent B as well as T cell activation. In contrast, the primary immune response lo test antigens is markedly decreased. To analyse these phenomena at a cellular level, we undertook a cross‐sectional study on 13 non‐active SLE patients and 15 controls. We determined the composition of lymphocyte subsets with special attention to activation markers (CD25, HLA‐DR, CD38) and the presence of naive T cells (CD45RO‐), and related those findings to serological parameters. In non‐active SLE patients the expression of activation markers on B cells and T cells was higher than in normal controls (P≤ 0·02), but was not interrelated. Percentages of activated B cells in SLB were related lo levels of total IgG (P < 0·02)and IgM (P < 0·02) but not to anti‐dsDNA, suggesting a disordered immune system also in clinically quiescent SLE. Numbers of CD4+ cells (P < 0·001) and CD4+CD45RO‐ cells (P < 0·05) were decreased. The latter finding might explain the anergy to primary test antigens in clinically quiescent SLE.