Obesity has a significant effect on the cephalic spread of a spinal block (SB) due to a reduction in cerebrospinal fluid (CSF). SB is controlled by the tissue blood flow in addition to the CSF. Some positions and techniques of surgery used can cause changes in hemodynamics. We investigated effects of hemodynamic changes that may occur during Transurethral prostate resection (TURP) and lithotomy position (LP) at the SB level in obese versus nonobese individuals. Sixty patients who had undergone TUR-P operation under spinal anesthesia were divided into a nonobese (BMI < 25 kg/m(2), Group N) or obese (BMI >= 30 kg/m(2), GroupO) group. SB assessments were recorded afterthe LP. SB at 6 and 120 min and the peak SB level were compared between two groups. Hemodynamics were recorded after LP. Peak and 6 min SB levels were similar between the groups, while 120 min SB levels were significantly higher for Group O (P < 0.05). Blood pressure (BP) after the LP was significantly higher for Group N (P < 0.05). LP and TUR-P increased the BP in Group N when compared to Group O. The increase in hemodynamics enhances the blood flow in the spinal cord and may form similar SB levels in nonobese patients to those in obese patients. However, SB time may be longer in obese patients.