This short review summarizes the use of late-night salivary cortisol measurement in the diagnosis of Cushing's syndrome, in the evaluation of patients with adrenal incidentalomas, and in monitoring of post-operative patients, with a focus on the different assay methodologies currently in common use. The focus is on recent studies identified by literature searches using Ovid Medline and Google Scholar as well as analysis of several recent review articles on the topic. Measurement of late night salivary cortisol (LNSC) has an excellent sensitivity and specificity for the diagnosis of Cushing's syndrome regardless of the assay methodology used. Immunoassays have the advantage of simplicity, low cost, and small sample volume requirement, while liquid chromatography-tandem mass spectrometry has the advantage of a high specificity for cortisol and the ability to measure cortisone. The overnight dexamethasone suppression test appears to be superior to LNSC measurement in the evaluation of patients with adrenal incidentalomas. LNSC measurement is an excellent approach to monitor post-operative Cushing's disease patients for surgical failure or recurrence. Salivary cortisol is most useful as the initial test when Cushing's syndrome is suspected and for periodic patient monitoring after pituitary surgery for Cushing's disease.