Capsaicin cream has been used to attenuate the pain associated with diabetic neuropathy, rheum-atoid arthritis, osteoarthritis and postherpetic neuralgia. But its common side effect, local irritation, limits the use of it and there is still a need for a new analgesic devoid of this side effect. This study was conducted to compare the local irritant effect of DA-5018, a new capsaicin derivative, with that of capsaicin in various animal models and human beings. Capsaicin, applied topically to the mouse ear, produced dose-dependent increase of ear volume and the frequency of ear scratching behavior in mice. Neither ear volume nor scratching behavior was affected by DA-5018. In eye wiping test of rat, DA-5018 was 10 times less irritant than capsaicin. Capsaicin administered intradermally into the rat paw elicited paw lick/lift response with a potency which was three times that of DA-5018. Zostrix-HP (0.075% capsaicin cream), but not DA-50180.3% cream, increased ear volume of rat and induced thermal hyperalgesia in normal and carrageenan inflamed paws. Six day-treatment of Zostrix-HP failed to develop tolerance against this thermal hyperalgesia. In human beings, Zostrix-HP produced burning sensation and itching in more than 90% of volunteers involved and its maximum irritant effect was significantly higher than that of DA-5018 cream. These results suggest that local irritation and burning sensation produced by DA-5018 is much less than capsaicin.