Neurofibromatosis type 1 (NF1) is a common inherited disorder. Neurofibromas may be situated almost anywhere in the body, including mediastinum, myocardium and autonomic nervous system. We, therefore, tested our hypothesis that arrhythmias would be more common during a 24-hour period in patients with NF1 than in control subjects. In a follow-up study of NF1 patients in Gothenburg, 38 out of 47 NF1 patients entered a study for comparison with 41 controls. We did not find any excess of arrhythmias. There were, however, fewer cases with episodes of bradycardia among the NF1 patients (p < 0.01) than among the controls. This might be explained by vagus nerve involvement.