This chapter presents lateral flow immunoassaysLateral flow immunoassays, from the first steps to future development trends. It covers the basic principles of this technology and detailed information on the biological and non-biological base components. Development schemesDevelopment schemes are presented, discussed, and linked to regulatory requirementsRegulatory requirements, also addressing the issue of intellectual property rights. The advantages and disadvantages of different assay formatsAssay formats are in focus as well as the different methods for signal evaluationSignal evaluation (qualitative, semi-quantitative, and quantitative) and the resulting requirements for the assay. The importance of this technology is finally underpinned with a brief market analysisMarket analysis, background information provides starting points for a further deepening of this topic.