Protein microarray technology allows the simultaneous determination of a large variety of parameters from a minute amount of sample within a single experiment. Assay systems based on this technology are currently used for the identification, quantitation and functional analysis of proteins that are of interest for proteomic research in basic and applied biology and for diagnostic applications. Such novel assays are also of major interest for the pharmaceutical industry, focusing on the identification of biomarkers and the validation of potential target molecules. Sensitivity, reproducibility, robustness and automation have to be demonstrated before this technology will be suitable for high-throughput applications.