The numbers of T lymphocytes, B lymphocytes, helper and suppressor T lymphocytes were measured in peripheral blood of patients with autoimmune disease (rheumatoid arthritis, erythema nodosum, Sjögren's disease, Wegener's disease, idiopathic thrombocytopenia, pernicious anaemia and Hashimoto's disease). B lymphocytes were enumerated by direct immunofluorescence and T lymphocytes by E rosette tests and by indirect immunofluorescence with OKT3.PAN Helper and suppressor T lymphocytes were determined by indirect immunofluorescence with OKT4.IND and OKT8.SUP respectively. The numbers of T lymphocytes, B lymphocytes and helper T lymphocytes in patients with autoimmune disease were normal, but the numbers of suppressor T lymphocytes were significantly lower.