Absorption, metabolism and excretion of 2-(5H-[1]benzopyrano-[2,3-b]pyridin-7-yl)propionic acid (pranoprofen), an anti-inflammatory drug, were investigated in mice, rats, guinea pigs and rabbits using 14C-labeled compound ( [14C]pranoprofen) at a dose of 5 mg/kg. After the oral administration of [14C]pranoprofen the radioactivity was rapidly and almost completely absorbed from the digestive organs of the animals tested. The radioactivity in the blood reached the maximum at 30--60 min after the oral administration of [14C]pranoprofen in all species tested, and the biological half-lives of the radioactivity were 4.1 h in rats, 2.6 h in guinea pigs, 1.3 h in mice and 0.9 h in rabbits, respectively. When [14C]pranoprofen was orally administered, urinary and fecal excretions of the radioactivity within 3 d were 81.1% and 18.7% of the dose in mice, 51.5% and 39.4% in rats, 81.8% and 9.0% in guinea pigs, and 93.2% and 3.6% in rabbits, respectively. A major metabolite of pranoprofen was its acyl glucuronide in rats, guinea pigs and rabbits. However, it was shown that acyl glucosidation is also a predominant metabolic pathway of pranoprofen in mice.