The objective of this pilot study was to evaluate the effectiveness of the fascia iliaca compartment block to control pain following total hip replacement by assessing pain intensity 24 hours after surgery and recording the use of opiates for rescue analgesia.We performed a prospective observational study of 41 patients undergoing total hip replacement surgery. The patients were divided into 2 groups: a group that received a fascia iliaca compartment block with 0.45% ropivacaine at a dosage of 0.3 mL/kg (maximum dose, 30 mL) and a control group in which no block was performed. Patients were enrolled consecutively as they entered the postanesthetic recovery unit. Postoperative pain was assessed on a visual analog scale (VAS) immediately after surgery and 24 hours later. Other variables recorded were opiate use for rescue analgesia and adverse effects due to the use of opiates.The VAS scores recorded in the postanesthetic recovery unit were significantly different in the 2 groups, with lower scores in the group receiving the fascia iliaca compartment block (P < .001). However, no significant between-group differences were observed in VAS scores recorded on the ward 24 hours after surgery (P = .57).A single-injection fascia iliaca compartment block was effective in controlling initial postoperative pain in a postanesthetic recovery unit. It was effective on the ward in the first few hours after surgery but not for the entire 24-hour period because of the limited duration of the block.