Little is known about the dynamic characteristics of stress system activity during "life as it is lived". Using as representative a study design as possible, this investigation sought to gain insights into this area. A healthy 25-year-old woman collected her entire urine over a period of 63 days in 12-h intervals (126 measurements) to determine cortisol and neopterin (immune activation marker) levels. In addition, she filled out questionnaires on emotional state and daily routine in 12-h intervals, and was interviewed weekly to identify emotionally negative and positive everyday incidents. Adjusted cross-correlational analyses revealed that stressful incidents were associated with cyclic response patterns in both urinary cortisol and urinary neopterin concentrations. Urinary cortisol levels first decreased 12-24 h after stressful incidents occurred (lag 1: -.178; p = 0.048) and then increased a total of 72-84 h later (lag 6: +.224; p = 0.013). Urinary neopterin levels first increased 0-12 h before the occurrence of stressful incidents (-lag 1: +.185; p = 0.040) and then decreased a total of 48-60 h following such stressors (lag 4: -.181; p = 0.044). Decreases in urinary neopterin levels were also found 24-36 and 48-60 h after increases in pensiveness (lag 2: -.215; p = 0.017) and depressiveness (lag 4: -.221; p = 0.014), respectively. Findings on emotionally positive incidents sharply contrasted with those dealing with negative experiences. Positive incidents were followed first by urinary cortisol concentration increases within 12 h (lag 0: +.290; p = 0.001) and then by decreases after a total of 60-72 h (lag 5: -.186; p = 0.039). Urinary neopterin levels first decreased 12-24 h before positive incidents occurred (-lag 2: -.233; p = 0.010) and then increased a total of 12-24 h following these incidents (lag 1: +.222; p = 0.014). As with previous investigations on patients with systemic lupus erythematosus (SLE), this study showed that stress system response can be considerably longer and more complex and differentiated than findings from conventional group studies have suggested. Further integrative single-case studies will need to be conducted in order to draw firm conclusions about stress system dynamics under real-life conditions.