Cortisol awakening responses (CAR) are often blunted or even extinguished when saliva samplings are delayed. The literature suggests that delays of 10 or 15min are tolerable. Delays of 15min were analysed with 510 CARs with the first sample taken within 3min post-awakening followed by 4 samples taken 15, 30, 45, and 60min later. Varying delays of up to 30min were analysed with these and further 148 CARs where sampling began within 30min post-awakening. Times of awakening and of saliva collection were verified by polysomnography or actimetry and by electronic devices respectively. Simulated sampling delays of 15min revealed highly significant deviations from correctly taken CARs. No deviations were found for delays of up to 11.5min suggesting that delays of up to 10min are acceptable but that delays between 10 and 15min might become critical.