Protein microarray technology has made enormous progress in recent years. It has been successfully applied for the identification, quantification and functional analysis of proteins in basic and applied proteome research. Protein microarrays have the potential to replace singleplex analysis systems. A variety of different analytical platforms have been developed that are likely to evolve into key technologies for the characterisation of complex samples. However, in contrast to well-established DNA microarrays, the robustness and automation needs to be demonstrated before protein microarray technology will reliably be integrated into high-throughput and routine applications. In this review we will summarise the current stage of protein microarray technology. Recent applications used for the simultaneous determination of a variety of parameters from a minute amount of sample will be described and future challenges of this cutting-edge technology will be discussed.