Aims. To measure blood and tissue concentrations of the H1-receptor antagonist, bepotastine besilate (BB). Methods. Participants included 14 men and six women, whose age ranged from 13 to 76 years, with chronic rhinosinusitis, who underwent endoscopic sinus surgery at our university hospital. Among them, 10 participants had allergic rhinitis (AR) (Group I), and others did not have AR (Group II). Nasal mucosa and blood were collected 55 to 130 minutes after oral administration of BB 10 mg. Concentrations of the agent in the serum and nasal mucosa were measured by high-performance liquid chromatography. Results. Concentrations of BB of the serum in Group I and II were 9 8 ± 3 2 ng/mL and 1 1 2 ± 3 9 ng/mL. Those of the nasal mucosa tissue in Groups I and II were 1 0 1 ± 3 6 ng/g and 1 3 2 ± 4 4 ng/g. There was no significant difference in the values of concentration of BB between the serum and the nasal mucosa in either Group I or II ( 𝑃 = . 7 5 7 and 𝑃 = . 2 6 6 2 , resp., Paired t-test). Conclusion. This preliminary study is considered the first report on the concentration of H1-receptor antagonists in nasal mucosa. The prompt absorption and transition to the nasal mucosa of BB seems to have an effect on allergic rhinitis.