Substance P and calcitonin gene-related peptides are involved in the process of the sensory reception and evoke vascular and glandular reflex reactions in nasal mucosa. The locations of both peptides in the nasal mucosa have been usually examined with cross sections. In order to observe the three dimentional distribution of each of the peptide-positive nerve fibers, we studied the presence of each peptide with the cross and tangential sections by indirect immunofluorescence technique in the nasal mucosa of rats. Aeticular network of the fibers containing SP or CGRP was observed in the lower portion of the mucosal epithelium. The single vertical fibers were also observed scattered among the epithelial cells. The fibers containing SP or CGRP, especially CGRP positive fibers, were observed next to blood vessels. This network may contribute to spreading of reflex reactions throughout the nasal cavity and may play important roles in the hyperreactivity of the nose.