A new serum cortisol assay was introduced on the Elecsys (Roche), a random access analyzer, with reportedly good performance in the low (nmol/L) concentration range (preliminary data provided by the manufacturer) and with low cross-reactivity with cortisone [0.3% at 2.7 μmol/L cortisone (package insert)]. This prompted us to evaluate the performance of this new assay for the measurement of salivary cortisol. For this study, saliva samples were collected with a Salivette® (Sarstedt), with an insert containing a sterile polyester swab for collection of the saliva, yielding a clear and particle-free sample. The salivettes were used according to the instructions provided by the manufacturer. Samples collected this way are stable at room temperature for at least a week and, therefore, offer the opportunity to collect samples at home (1)(2). Salivettes containing saliva were centrifuged at 2000 g for 10 min, and the filtrates were stored frozen (−20 °C). Before analysis, the samples were thawed, mixed, and placed on the Elecsys analyzer without pretreatment. The Roche cortisol assay is a competitive electrochemiluminescence immunoassay (ECLIA) that uses a sheep polyclonal antibody. Endogenous cortisol contained in the sample is liberated from …