Multiple sclerosis (MS) can cause alterations in autonomic cardiovascular functions. We aimed to investigate the correlation of disease activity and disability with heart rate variability (HRV) of cardiovascular autonomic dysfunction (CAD) demonstrated by 24-h Holter monitorization. Thirty-four patients with clinically active relapsing-remitting MS, age 33.8 +/- 7.6 years, were studied. Twenty healthy volunteers served as controls. The time domain long-term HRV parameters were recorded by a digicorder recorder calculated by ambulatory electrocardiograms.