The aim of the presented investigation was to identify different vanilloid receptor-1 (VR1) immunoreactivity after application of low dose of capsaicin (0.5 mg/kg) for a prolonged period in the rat's duodenum. Paraffin-embedded sections were processed for standard immunohistochemistry by the labelled streptavidin-biotin technique. The VR1 localisations were identified on the epithelial layers of the villi, in the Brunner's glands, smooth muscles layer, and the neurons of the myenteric plexus of the duodenum. While VR1 immunoreactivity was identified in small quantities in the control group, VR1 expression was strong both in the experimental and in the vehicle treated group. These results indicate that prolonged administration of a low dose of capsaicin may not be sufficient to stimulate VR1. Also the vehicle additives, Tween 80 and 10% ethanol, which are used to solubilize capsaicin, may activate the protection mechanism in the mucosa epithelium and stimulate the capsaicin sensitive afferent neurons by VR1 to increase mucus secretion.