OBJECTIVE: This study aimed to delineate cardiovascular autonomic modulation associated with overnight total sleep deprivation (TSD) in humans. METHODS: Cardiovascular autonomic modulation during overnight total sleep deprivation was assessed in 18 normal male subjects [age: (26.2 +/- 4.2) years, BMI (23.9 +/- 1.7) kg/m(2)]. ECG and continuous blood pressure from radial artery tonometry were obtained in seated position before TSD (baseline) and after overnight TSD. Spectral analysis of heart rate variability (HRV) and BP variability (BPV) were computed for cardiac parasympathetic modulation (high frequency power, HF); sympathetic modulation (low frequency power, LF), sympatho-vagal balance (LF/HF power of R-R variability, LF/HF) and BPV sympathetic modulation (low frequency power, BPV LF) in normalized (N) units [(total power of the components)/(total power-very low frequency power) x 100]. RESULTS: No significant changes were found in BP and heart rate. HRV LF was increased significantly from baseline (59.4 +/- 15.7)% to overnight SD (67.0 +/- 13.9)%. HRV LF/HF was increased significantly from baseline (2.7 +/- 1.7) to overnight SD (3.8 +/- 2.3), HRV HFN was decreased from baseline (29.0 +/- 11.6)% to overnight SD (22.8 +/- 10.4)%, BPV LF was significantly increased from baseline (63.2 +/- 16.5)% to overnight SD (72.4 +/- 13.2)%. CONCLUSION: Acute SD was associated with increased sympathetic and decreased parasympathetic cardiovascular modulation.