The analgesic efficacy of 50 and 100 mg tramadol and 500 and 1,000 mg metamizole was compared using a randomized double-blind design on 10 volunteers; drugs were given orally as solutions. Constant painful stimuli were applied by controlled electrical stimulation of tooth pulp. Analgesia was monitored by verbal pain rating, by measurement of the current necessary to evoke sensation in a tooth and with the aid of the amplitude of somatosensory evoked potential. All 3 algesimetric methods showed in complete agreement higher analgesia by the 100-mg dose of tramadol compared to all other medications; 50 mg tramadol and 1,000 mg metamizole were equipotent analgesic doses. The mean relative potencies of metamizole and tramadol were found to be 1:23 in agreement with clinical studies. Pain relief was limited to 3-4 h for 100 mg tramadol; 500 and 1,000 mg metamizole and 50 mg tramadol had a shorter period of analgesia.