We investigated the neurotoxic effects of capsaicin (CAP) on pain sensitivity and on the expression of capsaicin receptor, the vanilloid receptor (VR1), in rats. High-dose application of CAP has been known to degenerate a large fraction of the sensory neurons. Although the neurotoxic effects of CAP are well documented, the effects of CAP on the vanilloid receptor (VR1) are not yet known. In this paper, we investigated the effects of high-dose application of CAP on the expression of VR1 in rats. Thermal and mechanical pain sensitivity was reduced when neonatal rats were treated with a high dose of CAP. This reduction of pain sensitivity was significantly decreased after initiating carrageenan-induced inflammation. The expression of VR1 in dorsal root ganglia (DRG) isolated from the CAP-treated rats was reduced compared to that from the vehicle-treated rats. Therefore, we can conclude that the neurotoxic effect of CAP is related to the decrease of VR1 expression.