In a double-blind clinical trial the analgesic efficacy and safety of ethyl-N-(2-amino-6-[4-fluorophenyl-methylamino] pyridin-3-yl)carbamate (flupirtine, designated trademark: Katadolon) as 100-mg capsules were compared to pentazocine capsules 50 mg in 52 patients with severe to very severe cancer pain. The duration of treatment was up to one week, the daily dose up to 6 capsules. The analgesic effect was assessed by a 4-point verbal rating scale. In both drug groups was no difference between the baseline pain intensity. Moreover, also the dosage (number of capsules/day) was similar in both groups. Final evaluation demonstrated that flupirtine was significantly more effective than pentazocine in reducing pain. The incidence of side-effects was similar in both treatment groups, flupirtine, however, caused less intensive and less clinically relevant adverse reactions. In conclusion the results indicate that flupirtine is a potent and well tolerated analgesic in the treatment of cancer pain.