objectives: this study aimed to assess the impact of the duration of organ dysfunction on the outcome of patients with severe sepsis or septic shock. methods: clinical data were collected from hospital charts of patients with severe sepsis and septic shock admitted to a mixed intensive care unit from november 2003 to february 2004. the duration of organ dysfunction prior to diagnosis was correlated with mortality. results were considered significant if p<0.05. results: fifty-six patients were enrolled. mean age was 55.6 ± 20.7 years, mean apache ii score was 20.6 ± 6.9, and mean sofa score was 7.9 ± 3.7. thirty-six patients (64.3%) had septic shock. the mean duration of organ dysfunction was 1.9 ± 1.9 days. within the univariate analysis, the variables correlated with hospital mortality were: age (p=0.015), apache ii (p=0.008), onset outside the intensive care unit (p=0.05), blood glucose control (p=0.05) and duration of organ dysfunction (p=0.0004). in the multivariate analysis, only a duration of organ dysfunction persisting longer than 48 hours correlated with mortality (p=0.004, or: 8.73 (2.37-32.14)), whereas the apache ii score remained only a slightly significant factor (p=0.049, or: 1.11 (1.00-1.23)). patients who received therapeutic interventions within the first 48 hours after the onset of organ dysfunction exhibited lower mortality (32.1% vs. 82.1%, p=0.0001). conclusions: these findings suggest that the diagnosis of organ dysfunction is not being made in a timely manner. the time elapsed between the onset of organ dysfunction and initiation of therapeutic intervention can be quite long, and this represents an important determinant of survival in cases of severe sepsis and septic shock.