We examined spectral fractal characteristics of middle cerebral artery (MCA) mean blood flow velocity (MFV) and mean arterial blood pressure adjusted to the level of the brain (MAP_brain) during graded tilt (5 min supine, 10°, 10°, 30°, 60°, 10°, supine) in eight autonomic failure patients and age- and sex-matched controls. From supine to 60°, patients had a larger drop in MAP_brain (62 ± 4.7 vs. 23 ± 4.5 mmHg, P < 0.001; means ± SE) and MFV (16.4 ± 3.8 vs. 7.0 ± 2.5 cm/s, P < 0.001) than in controls. From supine to 60°, there was a trend toward a decrease in the slope of the fractal component () of MFV (MFV-) in both the patients and the controls, but only the patients had a significant decrease in MFV- (supine: patient = 2.21 ± 0.18, control = 1.99 ± 0.60; 60°: patient = 1.46 ± 0.24, control = 1.62 ± 0.19). The  value of MAP_brain (MAP_brain-; 2.19 ± 0.05) was not significantly different between patients and controls and did not change with tilt. High and low degrees of regulatory complexity are indicated by values of  close to 1.0 and 2.0, respectively. The increase in fractal complexity of cerebral MFV in the patients with tilt suggests an increase in the degree of autoregulation in the patients. This may be related to the drop in MAP_brain. The different response of MFV- compared with that of MAP_brain- also indicates that MFV- is related to the regulation of cerebral vascular resistance and not systemic blood pressure.