BACKGROUND Compartment syndrome of a lower extremity from hypoperfusion is a rare but potentially devastating complication of the lithotomy position during surgery. The aim of this study is to determine the effects of various lithotomy positions on lower-extremity blood pressures. METHODS Blood pressure in eight young, healthy people was studied for 10 lithotomy positions. Blood pressure measurements were taken in both the upper arm (brachial artery) and the lower extremity (dorsalis pedis). The heart-to-ankle height gradient in each position was measured, and a predicted lower-extremity systolic pressure was calculated. The measured and predicted lower-extremity systolic blood pressures were compared with repeated measures analysis of variance. RESULTS As a group, the mean systolic blood pressures in the lower extremities correlated closely with the predicted values. However, the difference between measured and predicted pressures varied among the 10 positions (P < 0.05). CONCLUSIONS Although lower-extremity systolic blood pressures in the young, healthy volunteers correlated with predicted values, there was an additional reduction in pressure associated with the lithotomy position. This surprising finding suggests that a lengthy procedure necessitating the use of a lithotomy position for only a portion should be planned so the remainder of the procedure can take place before establishing the position or so the position can be changed to an alternative position when it is no longer needed.