Regulatory control of diagnostic clinical laboratories activities has been defined in Italy since 1984, by an act (DPCM 10/2/84) that regulates such activities and establishes all over the country Quality Control (QC) programs. Before the 1984 act, External Quality Assessment (EQA) programs were exclusively conducted on a voluntary basis by Consiglio Nazionale delle Ricerche (CNR), by scientific societies, or by diagnostic manufacturers. The Subproject "Quality Control" of the Finalized CNR Project "Biomedical and Health Technologies", activated in 1982, is articulated in three fields: (1) EQA of the immunoassays, (2) EQA in the hematology laboratory and (3) EQA in radiodiagnosis. The problems of EQA have been also faced at the European level: initiatives, on both national and regional scale, have been promoted in the majority of the European States in the last ten years (Austria, Belgium, Denmark, Finland, France, Germany, Netherlands, United Kingdom, etc.) and include the main fields of the clinical laboratory analysis: hematology, clinical chemistry, immunochemistry, microbiology, cytogenetics, parasitology. The European Community plans the harmonization of the EQA programs starting from 1993, when reference preparations and commercial diagnostic kits will be subjected to free exchange and trade in the twelve Member States.