Using a food-reinforced two-lever operant procedure, rats (n=6) were trained to discriminate fentanyl (1.25 mg/kg, p.o., t-60') from solvent (1 ml/100 g B.W., p.o., t-60'). The administration of another narcotic analgesic (pethidine) produced a dose-related generalization with the standard fentanyl treatment; six non-narcotic analygesics (suprofen, acetylsalicylic acid, indomethacin, phenacetin, phenylbutazone, tolmetin) were found not to do so. It is concluded that the ability of drugs to produce analgesia is not a sufficient condition for the drugs to produce the narcotic cue as well.