Acetylcholine esterase (AchE) inhibitors are widely used to treat senile dementia of Alzheimer's type. The effects of two different AchE inhibitors on the autonomic nervous control of the heart were investgated in 47 patients (33 f, 14 m) with senile dementia of Alzheimer type: 14 patients (12 f, 2 m) received donepezil, 11 patients (7 f, 4 m) were treated with rivastigmine and 22 untreated patients (14 f, 8 m) served as controls. The root mean square of successive differences of R-R intervals (RMSSD), a time domain parameter of heart rate variability (HRV), was found significantly reduced in patients receiving rivastigmine (24.1 ms ± 17.6 ms; mean ± standard deviation) as compared to controls (40.1 ms ± 25.9 ms; p<0.05). There was a trend of HRV reduction in patients receiving donepezil, which did not reach statistical significance (27.6 ms ± 13.6 ms vs. 40.1 ms ± 25.9 ms; p>0.05). Heart rate and blood pressure were not found influenced by any of the AchE inhibitors. In conclusion, rivastigmine may inhibit cardiac autonomic control when given to patients with Alzheimer's Disease at therapeutic doses.