Because of interest in the link between oral and general health, clinicians are increasingly using salivary analyses to diagnose systemic disease and to monitor general health. The reason for this interest lies in the ability of new diagnostic tools, such as sensitive enzyme-linked immunosorbent assays, as well as other technologies, to distinguish a range of salivary components that are biomarkers for changes in the body's health. The noninvasive nature of salivary testing has made it an attractive and effective alternative to blood and urine testing, and home testing kits have made it possible for people to monitor their own health using this diagnostic medium. This paper explores what saliva can reveal about general health, drawing examples from recent research on salivary biomarkers of systemic illness and highlighting the current use, and potential clinical and research applications, of diagnostics based on oral fluids.