High-content analysis methods provide the opportunity to interrogate specific cellular end points in living cells. When coupled with high-throughput RNA interference (ht-RNAi) loss of function screens, high-content analyses are a powerful discovery tool for the identification of new genes and pathways involved in specific disease-relevant cellular functions. The most common readout is a fluorescence measurement, usually based on a green fluorescent protein reporter (or some derivative thereof  ) or a fluorescently labeled antibody. Here, we describe a specific approach to the development of a high-content assay for the hyperphosphorylation of tau protein that is compatible with RNAi screens. The goal of this chapter is to provide a generic paradigm, using hyperphosphorylation of tau protein as an example, to serve as a blueprint for the investigation of additional cellular end points or protein functions for those interested in performing high-content screens.