Autoimmunity is a such state of the immune system when in the sera of patients suffering on CTD-s permanently persist autoantibodies and autoreactive limphocytes T suspected to be involved in pathomechanisms of the disease. Beside, these autoantibodies are recognized as a ”markers” for particular disease. Since 1980, clinical investigators in the United States have been engaged in efforts to standardize reference sera for antinuclear antibody determinations. In 1980, the Arthritis Foundations in the United States in collaboration with the Centers for Disease Control established a Committee on Antinuclear Antibody Serology. In 1982, five reference reagents were made available. Following this initial activity several international organizations expressed support for expansion of these activities. These organizations were the ILAR, IUIS and WHO. The total number of reference reagents available in the CDC depository in 1988 comprised ten different sera. In 1988-89 laboratories in Europe have established active collaborations with the purpose of standardizing ANA methodology. Four laboratories from Eastern-Block countries establish in 1993/4 Eastern and Central Group European Consensus Workshop for Standardization of Autoantibodies to Intracellular Antigens. Department of Microbiology and Serology from the beginning actively participates in the projects of this Standardization Group, and in 1995 had organized in Warsaw Second Meeting of the CEECWSAIA. Department of Microbiology and Serology IR see evident benefits from the participation in the EFCS works and is dedicated to remain an active participants of the EFCS.