External quality control of laboratory work concerned with viral hepatitis (VH) and HIV virus which was started in the Czech Republic in 1993 comprises at the moment the opportunity to test 10 serological markers. During preparation of control samples the large number of commercial diagnostic tests must be taken into consideration as well as their different series of external quality control as regards the success of participants during the last roughly five years can be described as balanced, whereby between incorrect results caused by laboratory errors markedly false reactivities in negative samples predominate.

        Key words: external quality control, hepatitis B, hepatitis C, HIV