Production of the pro-inflammatory cytokine interleukin (IL)-17 by Th17 cells and other cells of the immune system protects the host against bacterial and fungal infections, but also promotes the development of rheumatoid arthritis (RA) and other autoimmune and inflammatory disorders. Several biologicals targeting IL-17, the IL-17 receptor, or IL-17-related pathways are being tested in clinical trials, and might ultimately lead to better treatment for patients suffering from various IL-17-mediated disorders. In this review, we provide a clear overview of current knowledge on Th17 cell regulation and the main Th17 effector cytokines in relation to IL-17-mediated conditions, as well as on recent IL-17-related drug developments. We demonstrate that targeting the Th17 pathway is a promising treatment for rheumatoid arthritis and various other autoimmune and inflammatory diseases. However, improvements in technical developments assisting in the identification of patients suffering from IL-17-driven disease are needed to enable the application of tailor-made, personalized medicine.