We measured the concentration of AM-715, a member of the pyridone carboxylic acid derivatives, in serum, tissue and secretion in 6 patients with chronic sinusitis and 5 patients with chronic otitis media. When administering 200 mg of the drug, the serum concentration was between 0.40 and 0.77μg/ ml, with an average concentration of 0.55μg/ml (n=9) after 2 hours. The average tissue concentrations reached 1.23μgg/g in maxillary sinus mucosa (n=5) and 2.36μg/g in middle ear mucosa (n=6). The average concentrations were 0.99μg/ml in maxillary sinal fluids (n=3) and 4.46μg/ml in otorrhea (n=3). The drug concentrations in the fluids thus reflect the drug concentrations in the respective tissues.