Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) recently moved from physics laboratories into diagnostic clinical microbiology.In this capacity it is currently replacing phenotypic bacterial identification tools that were designed and developed by Pasteur and Koch.Many European microbiology laboratories now use MALDI-TOF-MS with a high degree of efficiency.In the USA this will soon become common as well since the Food and Drug Administration (FDA) has now cleared the first of the commercially available systems for in vitro diagnostic use.This will also further spark the development of mass spectrometry applications in the field of antimicrobial susceptibility testing and epidemiological typing.This review summarizes the current state of affairs with respect to MALDI-TOF-MS in clinical microbiology.Emphasis will be on clinical relevance and studies in that field and the diagnostic data obtained through comparative analyses of different MALDI-TOF-MS instrumentation and through multi-center validation studies will be reviewed.