Dairy farmers need on-site, real-time information regarding mastitis occurrence in order to implement appropriate management actions. Technological progress has enabled the use of sensor systems as the basis for mastitis management. In this chapter, we describe the current state of automated mastitis detection systems in dairy cattle and potential new developments in mastitis detection. Most developed detection systems are focused on clinical mastitis, with systems utilizing electrical conductivity, on-line California mastitis tests, L-lactate dehydrogenase and on-line somatic cell counting being commercially available. The results of these systems are sufficient for practical use but not ideal. In the search for improved automatic mastitis detection, research is focused on: 1) improving existing and developing new sensors, 2) improving existing algorithms and combining more data sources within the analysis, and 3) defining specific mastitis situations for custom-made management measures.