According to the Regional Law n. 44 of 6/6/1988, all public and private laboratories in Tuscany, Italy, are obligated to carry out internal quality control and participate in external quality assessment programmes. The external quality assessment schemes are directly managed by "Regione Toscana" by means of the "Centro regionale di riferimento per la sicurezza di qualità". The programme for clinical chemistry (comprising cholesterol, glucose, urea, creatinine, sodium, potassium, calcium, uric acid, total proteins, ALT, AST, GGT) started in 1990 by sending two lyophilized serum samples from eight pools, each containing a different analyte concentration. In 1992 the analytes were increased to eighteen, chloride, phosphate, bilirubin, triglycerides, iron and alkaline phosphatase being added. At the same time the first cycle of the EQAs dedicated to the blood coagulation (including PT, APTT and fibrinogen) was started. In every cycle each laboratory must perform 16 analyses, by testing 8 pairs of samples from 8 different pools. The samples from different pools are sent by separate dispatches and in random order. Thus the participating laboratories receive and analyze the samples in a different sequence.