Antibody microarrays have enormous potential for becoming a tool that will allow, at the protein level, the type of global characterization of molecular mixtures that DNA microarrays already make possible at the RNA and DNA level. However, the much higher complexity of proteins both in terms of their sheer number and their structural and biochemical diversity necessitates an even more sophisticated analysis process. Its eventual realization will be demanding to achieve and requires further developments on many technical aspects, not in the least because the understanding of proteins is still comparatively less comprehensive than that of nucleic acids prior to the emergence of array technologies.