Saliva offers an alternative to serum as a biologic fluid that can be analyzed for diagnostic purposes. Whole saliva contains locally produced as well as serum-derived markers that have been found to be useful in the diagnosis of a variety of systemic disorders. Whole saliva can be collected in a non-invasive manner by individuals with modest training, including patients. This facilitates the development and introduction of screening tests that can be performed by patients at home. Analysis of saliva can offer a cost-effective approach for the screening of large populations, and may represent an alternative for patients in whom blood drawing is difficult, or when compliance is a problem . This review suggests that certain diagnostic uses of saliva hold considerable promise. Monitoring of the immune responses to viral infections, including hepatitis and HIV, may prove valuable in the identification of infected individuals, non-symptomatic carriers, and immune individuals. Saliva can also be useful in the monitoring of therapeutic drug levels and the detection of illicit drug use. Further, analysis of saliva may provide valuable information regarding certain endocrine disorders.