In a 84-day long-term study involving 20 patients with active Crohn's disease, the relation between daily stress and symptomatology was investigated. The diagnoses were verified clinically, endoscopically, radiologically, and histologically. The Crohn symptomatology was assessed by a daily symptoms diary. The degree of everyday stress was measured with a daily hassles scale. Additionally, the disease activity was measured 4 times. The data were evaluated using a time series analysis method following the ARIMA model (autoregressive integrative moving average model), which takes the autocorrelation of the data into account. In 55% of the cases, a significant correlation between daily hassles and disease activity was found. Patients whose symptomatology responded to stress did not differ from nonresponders in age, duration of the disease, disease activity, frequency of abdominal surgery, partnership situation, or statements concerning their average level of daily hassles. Disease activity in general did not change during the observation period. A verified influence of daily hassles on Crohn symptomatology as a rule occurs on the same day with time lag 0. According to these results, the group of Crohn's disease patients is not homogenous. The widely held assumption that daily hassles influence the symptomatology cannot generally be confirmed. Variations may result from different ways of coping with stress. Long-term effects of daily hassles on the disease are not clear.