BACKGROUND: Previous studies of heart rate variability (HRV) in systemic hypertension have yielded conflicting results. We sought to assess the alterations of HRV in hypertensive patients with or without left ventricular hypertrophy (LVH). METHODS: 195 hypertensive patients in sinus rhythm, mean age 53 +/- 11 years, without diabetes mellitus, nor symptomatic coronary disease or systolic dysfunction, were prospectively enrolled. Echocardiographic examination allowed their subdivision in 3 groups: normal geometry (112), concentric remodeling (43) and LVH (40). Time and frequency domain measures of HRV were obtained from 24 h Holter ECG recordings in all patients as in 40 control subjects. RESULTS: In comparison with control subjects, the 3 hypertensive groups presented a significant decrease of SDNN and total frequency power both indexes of global HRV; a significant decrease of pNN50 and high frequency power, indexes of HRV reflecting parasympathetic tone, and a significant decrease of SDANN and low frequency power, indexes reflecting sympathetic modulation of HRV. Comparisons among the three hypertensive groups showed that patients with LVH had significantly (p < 0.05) lower low frequency power (5.5 +/- 1.0 Ln m2) than patients with left ventricular normal geometry (5.9 +/- 0.8 Ln m2) or concentric remodeling (5.9 +/- 0.9 Ln m2). CONCLUSION: Assessment of HRV in hypertensive patients shows a constant decrease of parasympathetic indexes and a more markedly reduction of sympathetic parameters in presence of LVH.