The nocturnal excretion of catecholamines in urine was studied in 30-45-year-old women whose bedroom and/or living room were facing streets of varying traffic volume. The traffic volume of the streets was used as an indicator of noise exposure; adrenaline and noradrenaline concentrations were assessed as indicators of the outcome of the physiological stress. Significant associations between traffic volume and noradrenaline concentrations in urine were found with regard to the exposure of the bedroom (not the living room), indicating a higher chronic physiological arousal in noise-exposed subjects as compared to less exposed. Subjective measures of disturbance due to traffic noise were positively correlated with the noradrenaline level. However, this was only found in subjects where closing the window could not reduce the perceived disturbance, which points to the effectiveness of individual coping mechanisms. Stress hormones are useful indicators to study associations, mechanisms, and interactions between noise, health outcomes, and effect modifiers in epidemiological noise research.