Multiorgan dysfunction syndrome (MODS) and sepsis are two common clinical pictures of ICU patients, associated with a high mortality. The heart is compromised at MODS and sepsis. Clinically important is a pump failure of the heart; about the appearance and incidence of arrhythmias at sepsis and MODS is little known. The autonomic nervous regulation of the heart at MODS and sepsis is disturbed. Aim of this dissertation were the recording of rhythm disturbances of patients with MODS with or without sepsis at admission to an internal ICU ant the evaluation of the autonomic nervous regulation, determined by analysis of the heart rate variability (HRV). Diagnosis of MODS and sepsis was determined with APACHE-II-Score and Elebute Stoner Score. A Holter-ECG was performed to detect the arrhythmias and the heart rate variability of 61 patients. Patients with MODS show a significant increased incidence of atrial fibrillation compared to patients without MODS. An additional sepsis did not increase the incidence of arrhythmias. MODS is associated with a significant reduction of heart rate variability in the time and frequency domain, compared with healthy persons. The reduction of HRV correlates with the severity of illness. Patients, who died 28 days after admission on ICU showed a significant decrease of HRV shortly after admission.