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A variety of polypeptide growth factors are involved in the dynamic maintenance of the skin and hair. Here, we demonstrate the presence of high levels of fibroblast growth factor (FGF)-13 in the bulge region of hair follicles. Using real-time PCR, we found that expression of FGF-13 mRNA is comparable to, or higher than, that of other FGF known to regulate hair growth and wound healing. To gain additional insight into the function of FGF-13, we evaluated its distribution using in situ hybridization and immunohistochemical staining. Unlike other FGF, the distribution of FGF-13 mRNA and protein in adult mice was mainly restricted to cells in the bulge region of hair follicles, although lower levels were detected with less frequency in keratinocytes in the basal layer of the epidermis. FGF-13 protein was detectable in the bulge region throughout the hair growth cycle, but its distribution was especially wide during telogen and early anagen. During hair follicle morphogenesis in newborn mice, FGF-13 protein was first detected in the bulge region and basal layer keratinocytes 3 d after birth. These findings suggest that FGF-13 may play a role in regulating the function of cells in the bulge region and basal layer of the epidermis.