Two methods of evaluating analgesics, the hot-plate, and i.p. injection of HOAc, were compared.The analgesics were: aspirin, N-acetyl-p-aminophenol, phenacetin, salicylamide, cresopyrin, carisoprodol, isopropylpyrazoline, aminopyrine, phenylbutazone, cresotamide, noraminopyrine, quinine sulfate, all of them antipyretic analgesics, and morphine, palfium, and codeine, all of them narcotics.It is useful to combine the tests on the same animals.The chem. stimulus provides a better assessment of a weak analgesic action, while the thermal stimuli is to be preferred for a more powerful analgesic.