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Summary: Within the quality control scheme of the Deutsche Gesellschaft fur Klinische Chemie, seven quali-ty control surveys of thyrotropin (TSH) determinations in blood dried on filter paper have been carried outsince 1980. Ninety-six screening laboratories from 12 European countries took part in these surveys. In asingle survey each participant usually analysed four different samples; each of these consisted of three spots ofdried blood spiked with defined amounts of thyrotropin. For the evaluations of the surveys the participantswere asked to give Information about their analytical results, and from these, their diagnostic classifications.The medians of the analytical results correlated well with the given thyrotropin concentrations, but the indi-vidual estimations from different laboratories varied greatly. Major discrepancies of classification were alsoapparent, both in the given thyrotropin concentrations and in the individual estimations.Two special coHaborative studies with nine selected laboratories showed on the one band that analysis of thelafgest possible part of the dried blood sample can help to optimize the precision of the results; on the otherband, considerable drawbacks related to the reagents and the methods were sometimes observed.