This paper presents multi-scale fractal dimension (MFD) for the complexity assessment of heart rate variability (HRV) and systolic blood pressure variability (SBPV) under postural stress. A comparison of MFD with multi-scale approximate entropy (MAE) at multiple time scales (τ = 1 –10) is presented. The simulations were conducted on 50 random noise (RN), fractional Brownian motion (fBm), and MIX(p) [1] series along with standard EuroBaVar dataset. Also, 50 healthy volunteers, 20 post-acute myocardial infarction (AMI) patients participated in the study. It is observed that MFD and MAE decrease with τ for healthy volunteers and remained constant for post AMI and BRS failure patients. Average MFD of HRV in supine position is always significantly different than standing position scale except τ = 8 , whereas the average MAE of HRV shows no significant difference (p > 0. 0 5) between supine and standing postures at each τ except τ = 1 for healthy volunteers. Average MFD of HRV in supine position is significantly different than the standing position for τ = 1 –7, whereas the average MAE of HRV shows significant difference (p < 0. 0 5) between supine and standing postures at τ = 1 , 5 , 6 , 9 , 1 0 for post AMI, and patients with impaired baroreflex sensitivity (BRS). Average MFD of SBPV in position is significantly different (p < 0. 0 5) than standing position at each τ , whereas the average MAE of SBPV shows no significant difference (p > 0. 0 5) between supine and standing postures at each τ except τ = 2. The complexity of HRV in standing position is less than that of supine position as shown by lower MFD and MAE values in standing than that of supine position, however, the complexity of SBPV decreases from standing to supine position indicating prevalence of sympathetic control. [ABSTRACT FROM AUTHOR]