A femoral nerve block was performed as a postoperative analgesic technique in 50 patients after knee surgery; this surgery is a very painful one. The technique used was the inguinal route, as described in the textbooks. Bupivacaine was used: 1.5 mg X kg-1 without exceeding 150 mg. The result was good in 46 patients, with four failures. The average duration of analgesia was 600 min, the shortest being 300 min, the longest being 1,200 min. This technique can be recommended after surgery of the knee as safe and reliable.