Protein arrays are lagging behind in their implementation relative to DNA arrays because proteins are harder to produce and keep active. But in the September Nature Biotechnology de Wildt et al. describe the use of robotic spotting to produce antibody arrays, using bacterial colonies that produce single-chain antibodies (Nat. Biotechnol. 2000, 18:989-994). Up to 18,342 antibody clones can be screened at one time, and the same antibody-producing cells can easily be spotted onto up to 15 replicate filters. Although the current set-up is valuable for evaluating antigen-antibody interactions, an array that could be used for a comprehensive proteomics application is still a long way off.