This short course is targeted at those who wish to learn the basics and challenges of drug screening on information rich cell based models. Cell-based assays, because of their advantages in terms of predictability, multiplexing, miniaturization and automation seem the most appealing tool for the high demands and high quality standards of the early stages of the drug-discovery process. Nevertheless,scientists working on assay development for cellular screening still face a variety of challenges. Aspects of assay design ranging from cell type choice, readout selection, standardization, miniaturization, data analysis, will be covered. Moreover, advantages of targeted versus phenotypic assays in drug screening will be discussed.