Many autoimmune diseases are chronic diseases characterized by the presence of autoantibodies that precede clinical findings by months or years. Autoantibodies may also predict specific clinical manifestation, disease severity, and rate of progression. Combining serological arrays with specific genetic test and HLA typing may allow a more accurate assessment of autoimmune disease risk. The implications of such findings are the prediction and possible prevention of autoimmunity. Autoimmune diseases have been long recognized as chronic and complex disorders, characterized by the presence of circulating antibodies that bind self-protein. With progress in technology and availability of laboratory tests, it has gradually become apparent that autoantibodies are present in the sera of "healthy" or rather asymptomatic individuals. Advanced technologies such as the multiplexed assay system and proteomic microarray may enable mass testing for autoantibodies, and perhaps future screening programs. However, both practical and ethical issues remain to be resolved for such prospect to materialize. This chapter emphasizes on the role of autoantibodies as predictors of autoimmunity, as well as on the practical implications of this role.