The recent introduction of molecularly targeted anticancer therapeutics has revealed a great need for a new class of clinical bioassays. The shift from cytotoxic chemotherapy to biomolecular therapeutics requires that efficacy is assessed at the biologically active dose that modulates the target, rather than using the conventional dose-toxicity relationship. In this context, functional cytomics is slowly becoming an omnipotent part of the post-genomic drug-discovery pipelines. Although, it is widely recognized in the drug-discovery arena that the validation of therapeutic targets revealed by proteomic and genetic screens requires functional cell-based assays, their widespread clinical applications are still underdeveloped. In this context, microfluidic cell array technologies provide important technological advances that allow for fundamentally new capabilities in the spatiotemporal control of molecules and cells. Pioneering lab-on-a-chip devices, such as microfluidic cell arrays, allow for a lucid integration of multiparameter data, obtained from functional cell-based assays, as well as from proteomic and genetic screening. They also offer opportunities for fabrication of parallelized and fully addressable perfusion microarrays aiming at greatly reduced equipment costs, simplified operation, increased sensitivity and throughput by implementing, for example, a parallel processing principle. Lab-on-a-chip microfluidic cell arrays therefore provide new opportunities for the development of content-rich personalized clinical diagnostics and higher-throughput clinical screening in oncology.