In some conditions e.g. osteoporosis, hypertension and hypercholesterolaemia, certain phenomena precede manifestation of the disease and preventive measures can be taken long before the disease presents itself. In the same way systemic lupus erythematosus (SLE) and rheumatoid arthritis can be explored. Recently, studies have been published on healthy blood donors, who later developed SLE or rheumatoid arthritis, and in whom specific autoantibodies could be demonstrated. In SLE the autoantibodies are not specific enough to develop preventive strategies, but in rheumatoid arthritis in particular there are specific antibodies against cyclic citrullinated peptides (anti-CCP-antibodies) which are very specific. A clinical trial has been initiated in which HLA-DR4-positive people with raised autoantibody concentrations are given 1-2 intramuscular injections of dexamethasone with the aim of halving the antibody concentration and in the long term lowering the incidence of rheumatoid arthritis.