Tandem mass spectrometry is a new technology used in newborn screening of inborn errors of metabolism. This technology significantly increases preventive effect of newborn screening. It enables to screen simultaneously within the same analytical run not only phenylketonuria but also 24 others inborn errors of metabolism from a dried blood spot. The early diagnosis and treatment are now possible by to date late or no diagnosing disorders. The overall incidence of detectable inborn errors of metabolism bymeasurement of amino acids and acylcarnitines is 1:4500.

        Key words: inborn errors of metabolism, newborn screening, tandem mass spectrometry