Total knee replacement (TKR) is one of the most painful orthopedic surgical procedures. This study was aimed to investigate the effect of a single-shot preoperative 3-in-1 femoral nerve block on postoperative pain by using 0.375% ropivacaine, and on the consumption of morphine by using PCA following the TKR surgery. Side effects were also evaluated in this setting. 34 patients were included in this study. Group R (n=17) received a 3-in-1 femoral nerve block (FNB) with 40 mll of ropivacaine 0.375%. Group S (n=17) received only a 2 mg loading dose of morphine 30 minutes before the end of surgery, and no block was performed. Both groups received general anesthesia and postoperatively had a PCA pump programmed to deliver morphine. VAS scores at rest, morphine consumption and adverse effects were recorded. Two patients were excluded from each group. Pain scores at 0, 1, 2, 3, 4, 6, 8 postoperative hours were significantly lower in group R in resting position (p<0.05). Group R experienced no pain at the recovery room and this state lasted 8 hours after the surgery while group S reached the acceptable score (VAS ? 3) one hour after leaving the recovery room. The morphine requirement was significantly lower in Group R at 12, 18, 24, 48 hr after TKR (p<0.001). Side effects were also lower in this group. Preoperative single-shot 3-in-1 FNB with 40 cc of ropivacaine 0.375% provides better VAS scores, less morphine consumption and fewer side effects in elderly patients when compared to the group with no block.