Introduction : HYENA (HYpertension and Exposure to Noise near Airports), a well-known study on the health effects of aircraft noise, involved 4,861 participants from six European countries (except France). DEBATS (Discussion on the health effects of aircraft noise), a study with a similar protocol, included 1,244 participants from France. Saliva samples were obtained for 439 and 954 participants in HYENA and DEBATS respectively, to determine cortisol concentration as a possible marker of noise-induced stress. Associations were found between aircraft noise and cortisol levels in each study separately, but they were not consistent between the two studies. The objective of the present study was to combine datasets to improve statistical power. Methods : We investigated the associations between aircraft noise levels and, the log-cortisol levels in the morning and in the evening, and the log-relative variation per hour, adjusted for relevant confounders. Results : We found evidence in women for an increase in the log-evening cortisol level ?=0.09 (95%CI 0.01;0.17), and for flattening of the log-relative variation per hour ?=-0.09 (95%CI -0.16;-0.02), with a LDEN 10-dB(A) increase, but no significant effects in men. Conclusions : These findings provide some support for psychological stress induced by aircraft noise exposure, resulting in disruption of hormonal rhythms.