Transfected cell microarrays, arrays of cells expressing defined cDNAs, are promising technologies that can enable the functional analysis of many proteins in parallel. This technique has been adapted for the comparative functional analysis of single-chain antibodies (scFvs) and to facilitate the screening and characterization of these antibodies for their use in diagnostic and therapeutic applications. In this method, membrane-targeting expression vectors encoding scFvs are mixed with transfection reagents and are deposited at high density onto a microscope slide. Adherent mammalian cells are subsequently added to the printed array. Upon attachment to the substrate, the cells take up the plasmid DNA and express the particular protein encoded at each location. The result is an array whose features are micrometer-sized clusters of cells expressing defined genes. This approach provides for the high-throughput functional analysis of many different proteins in parallel and can be considerably more informative and cost-effective relative to more traditional protein expression techniques.